Road Tunnel Manual-piarc

176,0-Preface-EN-v-05.09.2011.pdf 99,Chap-0-Introduction-EN-v-02.09.2011.pdf 357,Chap-1-Strategy-EN-v-21.09.2011.pdf 211,Chap-2-Safety-EN-v-06.09.2011.pdf 217,Chap-3-Human-factors-v-06.09.2011.pdf 236,Chap-4-Operation-and-maintenance-EN-.pdf 153,Chap-5-Environment-EN-v-06.09-2011.pdf 244,Chap-6-Geometry-EN-v-30.08.2011.pdf 223,Chap-7-Structural223,Chap-7 -Structural-facilities-EN-vfacilities-EN-v-07.pdf 07.pdf 257,Chap-8-Equipment-and-systems-EN-v-21.pdf 262,Chap-9-Response-to-fire-EN-v-07.09.2.pdf 164,Glossary-EN-v-07.09.2011.pdf

ROAD TUNNELS MANUAL

PREFACE

All rights reserved. © World Road Association (PIARC).

PIARC ROAD TUNNELS MANUAL

© PIARC

Preface This Road Tunnels Manual, in electronic version, is a major achievement of the technical committee C.4 Road C.4 Road Tunnel Operations, Operations, during the operating cycle 2008-2011, under the decisive leadership of its president Pierre Schmitz (Belgium). This work makes it possible to make available in readily accessible form the knowledge and recommendations hitherto published, by the World Road Association, in the form of separate reports. The organization in the form of Web pages facilitates the access to information and will also in the future make it possible to more easily update the contents in accordance with the progress of knowledge. The version put on line at the time of XXIV World Road Congress in Mexico City, in September 2011, is a first version of this Manual. Initially, the contents of the old reports will remain accessible by the means of links towards the PDF files from these documents. Later on, when the contents of these reports are updated, the text will be recast in the form of Web pages to improve reader convenience. In order to give a broad audience to this Manual, which is without equivalent in its field, the electronic version is produced and will be maintained, by the technical committee in the two official languages of the Association: English and French. Nevertheless some countries have expressed an interest to have a version of the Manual in their own language; thus versions are under development in Spanish, Chinese, Japanese, Korean and Czech on the initiative of various organizations and with the assistance of the technical committee. We make a point of encouraging such initiatives which must be expressed to the Secretary General of the World Road Association, who will guide the proposals. We hope that this Manual will be an indisputable reference in the whole world, and that i t translates, in an objective way, the best practices and knowledge at the moment. For that we need your remarks and suggestions in order to improve and to update this Manual. Good reading and thanks in advance for your comments and suggestions,

Jean-François Corté Secretary General World Road Association

August 2011

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ROAD TUNNELS MANUAL

0. INTRODUCTION



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Introduction 1. Origins and objectives of the Manual Road tunnels are increasingly used to cross natural barriers such as mountain ranges, rivers, straits or bays. They also constitute a solution, sometimes the only one, to the environmental and spatial constraints of the urban environment, where in the future three-quarters of the global population will live. Under these conditions, the construction and the maintenance of a tunnel are always a challenge and their realisation requires the use of techniques and tools that are increasingly sophisticated and complex.

Fig. 0-1 : C4 Committee meeting in Madrid (March 2009)

The need for bringing together the experiences gained in the field of the tunnel operations goes back several decades already. This is why, in 1957, PIARC created the "Road Tunnel Committee" to address the range of aspects concerned in the use of road tunnels, such as geometry, equipment and its maintenance, operation, safety and environment. Since then, supervised by successive presidents and with the help of the secretaries (see list below), this committee has produced technical recommendations across all of these various fields. President

French-speaking secretary

Englishspeaking secretary

Spanishspeaking secretary

From 1957 to 1975

Jacques Rerolle (France)

Fernand Ramel (France)

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From 1976 to 1979

Jacques Rerolle (France)

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From 1980 to 1991

Sir Alan Muir Wood (UK)

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From 1992 to 1995

Emanuele Scotto (Italy)

G.R. Fellowes (UK)

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From 1996 to 1999

Michel Marec (France)

Alan West (UK)

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From 2000 to 2003

Didier Lacroix (France)

Alan West (UK)

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From 2004 to 2007

Didier Lacroix (France)

Pierre Schmitz (Belgium)

Alan West (UK)

Manuel Romana (Spain)

From 2008 to 2011

Pierre Schmitz (Belgium)

Alexandre Debs (Canada-Quebec)

Robin Hall (UK)

Ignacio Del Rey (Spain)

Claude Bérenguier (France) Claude Bérenguier (France) Michel Marec (France) Willy De Lathauwer (Belgium) Willy De Lathauwer (Belgium)

Table 0-2 : List of the road tunnel committee presidents and secretaries

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These recommendations are substantially followed worldwide and they are even often used as the basis for contractual specifications in many countries. In 1974, ITA (International Tunnel and Underground Space Association) was created to address aspects of the construction of all types of underground works, including road tunnels. In 2005, a Memorandum of Understanding was concluded between these two international associations to ensure that their actions are and will remain complementary and not overlapping. Since its creation, the "Road Tunnel Committee", which was renamed the "Technical Committee for Road Tunnel Operations" in 1996, has taken part in 14 World Road Congresses. For the first 5 of them, from 1959 to 1975, it published several hundreds of pages of documentary materials. From 1971 (the Prague Congress) onwards, the committee released an up-to-date summary report that listed recommendations on all of the topics examined during each cycle. Since the Kuala Lumpur Congress in 1999, these summary reports were replaced by introductory assessments for each Congress session organised by the committee. In 1995, the committee started to issue PIARC reports outside of the Congresses. The first of them was the special report "The first Road Tunnel" authored by Sir Alan Muir Wood under the aegis of the committee and published in 1995 with the intention of reaching tunnel designers in countries facing the prospect of introducing tunnels in their road networks. Since then, 32 other reports have been published or are in preparation. All these Reports are available free of charge on the PIARC Website. In addition to these outputs of the committee, many articles have been published in Routes/Roads, notably the October 2004 special issue 324 written in collaboration with ITA and entirely devoted to fire safety in tunnels. The tunnel committee was also involved in the ERS2 research project, undertaken jointly from 1997 to 2001 by OECD and PIARC, on dangerous goods transport through road tunnels. A Quantitative Risk Assessment Model (QRA Model) was developed within the framework of the ERS2 project. During the preparation of the centenary Congress in Paris in September 2007, the members of the committee discussed the interest there would be in gathering, synthesising and if necessary updating the large quantity of information disseminated in these various reports and articles. During the Paris Congress, it was decided that this idea would be proposed at the PIARC executive committee for the next cycle of the Road Tunnel Operations committee. This proposal was adopted and the committee was requested, within the 2008-2011 cycle, to produce an electronic encyclopaedia, which would be hosted on the PIARC Website.

2. Contents of the Manual

This electronic encyclopaedia, called the "PIARC Road Tunnel Manual", primarily takes the contents of the 35 reports issued by the committee between 1995 and 2011, the twenty or so most recent articles published in Routes/Roads in the field of tunnels plus the documents of the joint OECD/PIARC research project. It also links to several useful sites. Fig. 0-3 : Tunnel Calle 30 in Madrid (Spain) Just like the PIARC Road Tunnel Operations Committee, this Manual exclusively concerns the operational aspects of these works (geometry, equipment and its maintenance, operation, safety,


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PIARC ROAD TUNNELS MANUAL environment). It does not consider the civil engineering aspects of tunnels (geology, geotechnics, structures, coatings, waterproofing, drainage, etc), except with regard to their effects on the operation and maintenance of the road tunnels The Manual comprises two principal parts. The first part considers general aspects of road tunnels. Chapter 1 presents the principal strategic elements of which any decision maker must take into account before making a decision concerning the choice or the design of a tunnel. This chapter is addressed particularly to the decision makers and to the designers of countries that are starting to tackle the construction or major refurbishment of a tunnel. Chapter 2 deals with the crucial topic of safety in tunnels. In particular, it considers methods for risk analysis. Chapter 3 considers the human aspects that affect the operation of road tunnels. The severe fires in 1999 and 2000 confirmed how important it is to take human behaviour into account at the design stage. Chapter 4 examines the management and the maintenance of tunnels for which, in addition to safety, durability is a key concern. Chapter 5 deals with the environmental aspects of road tunnel operations, not only in terms of air pollution but also noise and water pollution. The second part of the Manual addresses particular elements of tunnels taking operational and safety requirements into consideration. Chapter 6 addresses the geometrical characteristics of the tunnels and their influence on operation and safety. Chapter 7 deals with the structural facilities that support operations and safety and must be taken into account at the early stages in a tunnel project, and whose impacts should not be underestimated, particularly on costs. Chapter 8 reviews the different types of tunnel equipment and gives recommendations covering the whole of their lifecycle. Lastly, Chapter 9 addresses the performance of materials, structures and equipment in fire. The Manual ends with a Glossary showing the contents of the PIARC Tunnels Dictionary. This Manual was designed to be a "live" document in order to be able to follow the frequent technological developments that are adopted from the design to the operation of the tunnels, and to be able to easily integrate the new reports that will be produced by the committee during following cycles. In this first version (2008-2011), the committee members have primarily endeavoured to define the structure of the Manual and to integrate into it, by means of new text or hyperlinks, the most relevant documents that already exist. Later, the old texts will be up-dated and up-graded as necessary and on this occasion the integration of their content within the Manual will be examined when appropriate.

3. Contributors The preparation of the first version of this Manual was coordinated by Working Group 5 of the C4 committee (2008-2011) in which: 

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Pierre Schmitz (Belgium), president of the committee, assumed the coordination of the working group, carried out the electronic pagesetting of the Manual, wrote the introduction and the home page, supervised the Glossary; Bernard Falconnat (France) wrote chapter 1;

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Fig. 0.4 : WG5 meeting in London

Didier Lacroix (France), former president of the committee, reviewed all the French texts, checked their accordance with the English texts and supervised the writing of chapter 2;


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Willy De Lathauwer (ITA), former French-speaking secretary of the committee, supervised the writing of chapters 3 and 6; Roberto Arditi (Italy) supervised the writing of chapters 4 and 5; Robin Hall (UK), English-speaking secretary of the committee, reviewed all the English texts and supervised the writing of chapters 7 and 9; Antonio Valente (Italy) supervised the writing of chapter 8; Rafael López Guarga (Spain) managed and supervised the translation of the encyclopaedia pages in Spanish.

4. Future evolutions and thanks In order to help the committee to improve this Manual, all your comments and suggestions are welcome. You can forward them just by clicking on "Contact" at the top of a page of the Manual. We want to thank all those who have contributed to the realisation of this Manual and in particular all members of the preceding tunnel committees which wrote the reports on which this Manual is based and whose names appear at the beginning of those reports. The contributors of the committee and its working groups to the writing of the various chapters of the Manual appear in bottom of the introductory page of each one of these chapters. We hope that this Manual will constitute a useful and convivial reference work for all those who are concerned with road tunnels. We hope that this Manual can meet their needs and, with the comments and suggestions of its readers, that following tunnel committees can improve this Manual so that it becomes for all a valuable tool which helps to support the effective and safe transport of goods and people in road tunnels thanks to the contributions of all the PIARC committees members who will have contributed to it.

Pierre SCHMITZ President of the PIARC Technical Committee C4 Road Tunnel Operations (20082011) Ministry of the Region Brussels Capital - Brussels Mobility Brussels (Belgium) September 2011


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ROAD TUNNELS MANUAL

1. STRATEGIC ISSUES



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1. Strategic issues Tunnels, initially aimed at crossing an obstacle (in general a mountain), have become increasingly complex during recent years, incorporating increasingly complex equipment (including ventilation systems) and methods of operation. Such operation includes the deployment of control and supervision systems that able to handle tens of thousands of items to be controlled, and which can accommodate increasingly sophisticated management scenarios. Following the catastrophes at the Mont Blanc, Tauern and Gothard tunnels in the years 1999 and 2001, the need for recognising all aspects relating to safety as a holistic system was reinforced. This resulted in the integration, from the design of the works onwards, of more constraining provisions, which have an important impact on the required civil engineering and the specified tunnel equipment. Tunnels are in general considered as "expensive and risky" works, both with regards to their Figure 1.0 : St Gothard tunnel fire construction as well as their operation. This "image" makes some countries very reluctant when considering the construction of their first tunnel for their road or railway infrastructure. In order to address such concerns, it is inevitable that the costs of construction and operation, the control of risks (mainly during the construction phase), the minimisation of accidents or fires during the operation and the optimisation of the tunnel facilities at each stage of the design, construction and operation become increasingly necessary.This control of the risks and the costs is reinforced when considering current procurement and financing models for the construction of tunnels, which are increasingly being implemented as "Concession", "Design and Build" or "Private Public Partnership" models. Chapter 1 of this manual has the following aims: 

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to make the reader aware of the "complex system" that a tunnel comprises; to highlight the importance of the definition of the "function" of the facility for both the upstream (design) and downstream (operational) aspects of the design; to draw the attention of the tunnel owner to the need for surrounding himself with multidisciplinary competences with skills and in-depth experience to ensure the success of the mission; to make the reader aware that a tunnel is essentially designed to be used in conditions of comfort and safety, and that it must be the subject of continuous and reliable maintenance by the operator. The concept of a tunnel must take into account these safety and operational objectives and constraints; and finally to make the reader understand that the facility itself constitutes only a part of the problems which the owner will have to solve, and that very often it will be necessary to develop in parallel certain external elements which may be outside the tunnel owner’s authority: regulation, intervention and safety services, procedures, etc.

It is not the intention for Chapter 1 to be a detailed handbook of the actions required by tunnel owners, or to specify the technical provisions to be implemented by the designers, or to determine the tasks to be taken by the operators to ensure a safe and comfortable tunnel. In particular, Chapter 1 does not have an objective to be a handbook of design. Its only objective is to make the reader aware of certain issues, in order to facilitate his approach and comprehension of this complex field, to hopefully enable him to avoid the many possible errors in tunnel operations, and to enable him to perceive the possibilities of optimisation.

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Section 1.1 presents the "complex system" that a tunnel is, and lists the main interfaces of the various subsets Civil Engineering, Ventilation and Safety; Section 1.2 presents the major elements which have t o be considered when designing a tunnel; Section 1.3 concerns the upgrading and the refurbishment of existing tunnels under operation; Section 1.4 analyses various stages of the cycle of construction and the life cycle, and underlines the key actions of each one of these phases; Section 1.5 explains issues relating to the costs of construction, operation and renovation, as well as the main stakes specific to the modes of financing; Section 1.6 gives a list of the main recommendations, instructions and regulations published by a number of countries in Europe and in the world.

Contributors This document was compiled by Bernard Falconnat (Egis, France), French representative in the Road Tunnels Operation Committee and member of Working Group 5, which has also translated his French version into the present English version. Its original version in French was revised by Didier Lacroix (France) and Willy De Lathauwer (Belgium – ITA representative within the committee). The English version has been reviewed by Lucy Rew (Egis, France) and Fathi Tarada (UK).

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1.1. Tunnel is a complex system

1.1.1. Complexity of the system A tunnel constitutes a "complex system" which is the result of the interaction of very many parameters. These parameters can be gathered by subsets, the principal ones of which are represented on the graph below (fig. 1.1-1). All these parameters are variable and interactive, within each subset, and between the subsets themselves. The relative weighting of the parameters and their character varies according to the nature of each tunnel. For example: 

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the determining criteria and the weighting of parameters are not the same for an urban tunnel and a mountain tunnel; the parameters differ for short and long tunnels, for tunnels passed through by vehicles transporting dangerous goods and for those transporting passenger vehicles only; the criteria are not the same for a new-build tunnel or a tunnel to be refurbished or upgraded to put it in conformity with new standards concerning safety.

Fig. 1.1-1 : Sketch of main subsets of the "complex tunnel system" Note 1: the links are multiple and often reversible - the general concept of the tunnel and the functional section are placed in the centre of the figure. Similar diagrams could be drawn up while placing other factors in the centre of the figure. Note 2 : the first circle represents "technical fields". Some fields represent multiple aspects: 

safety: regulation - risk analysis - intervention means - requirement of availability,

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geology: geology - geotechnics - structural dimensioning, civil works: methods - construction schedule - risks and hazards, operation: operation and maintenance (technical aspects), costs: construction - operation - daily maintenance - major repairs, environment: regulation - diagnosis - impact assessment - treatment and mitigation,

Note 3: the second circle represents the "context" in which the project is to be developed. Some elements represent multiple aspects:   

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human environment: sensitivity - urbanisation - presence of buildings or infrastructure, natural environment: sensitivity - water - fauna - flora - air quality - landscape, nature of the transport: nature and volume of the traffic - typology - types of goods that are transported - etc. various external constraints: accesses and particular constraints - climatic conditions - avalanches - stability of the ground - socioeconomic context - etc. level of profitability: economic acceptability - capacity of financing - control of the financial costs general economic and political context in case of concession or Public Private Partnership (PPP).

The design of a new tunnel (or the refurbishment and upgrading of an old tunnel) requires these numerous parameters to be taken into account. The decision tree relating to these parameters is complex, and requires the input of experienced multidisciplinary parties. They must intervene as early as possible, for the following reasons: 

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to enable all relevant parameters to be considered from project commencement, and to avoid numerous potential pitfalls noted in projects in progress or in recently completed tunnels. Such errors include the late consideration of the required equipment for operation and safety, and the development of a supervision system without integrating the results of the risks analyses, the emergency response plan or the operation procedures.As a consequence, the tunnel and its systems and equipment for operation and supervision may be inappropriate for safe and reliable operation. an early intervention contributes to a better optimisation of the project, both from the perspective of safety as well as for construction and operation costs. Recent examples indicate that transverse optimisations (civil engineering - ventilation - safety evacuation) made at early project stages can contribute about 20% towards cost savings.

Each tunnel is unique and a specific analysis has to be developed, while taking into account all the specific and particular conditions.This analysis is essential to bring suitable answers and to allow:   

optimisation of the project from a technical and financial aspect; reduction of the technical, financial and environmental risks; guaranteeing the required level of safety for tunnel users.

There is no "magic key solution", and a simple "copy and paste" process is almost always unsuitable. The design and optimisation of a tunnel require:   

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an exhaustive and detailed inventory of all the parameters, an analysis of the interactions between parameters, the evaluation of the degree of flexibility of each parameter, and if necessary of the sensitivity of each one of them with respect to the required objectives, a holistic approach to achieving success, because: - a purely mathematical approach is not possible, owing to the fact that the "system" is too complex, and there is no single answer; - too many parameters are still unspecified or variable during the early stages of a project, but essential choices still have to be made; - the evaluation of the risks, their gravity and their likelihood of occurrence must be taken into account; - many parameters are interdependent and many interactions are circular.

Several examples are given in the following paragraphs making it possible to clarify the complexity, the interactivity, as well as the iterative and "circular" character of the analysis.


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These examples are not exhaustive. Their aim is simply to make the reader aware of the issues and make it possible to focus considerations on each specific tunnel.

1.1.2. Subset "Civil Engineering" 1.1.2.1. Parameters Table 1.1-2 below gives an example of the principal parameters concerning the aspects relating to civil engineering:

Table 1.1-2 : Main parameters according to civil engineering 

The first column of the table indicates the principal sets of parameters,


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The second column of the table indicates the principal subsets of parameters relating to a principal set, The third column lists a certain number of elementary parameters relating to a subset. The list is not exhaustive, The fourth column of the table indicates by set, or subset, the principal outcomes related to the subset.

1.1.2.2. Interactions between parameters The interactions between parameters are numerous and often connected by circular links taking into account the overlaps between the various parameters. The example below (Table 1.1-3) relates to the interactions between ventilation, the cross section, and safety: 

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The first column concerns ventilation. The parameters listed in this column are the elementary parameters resulting from table 1.1-2 above for the subset "ventilation", The second column concerns the cross section. The parameters result from table 1.1-2, The third column concerns safety.

Table 1.1-3 : Interactions between parameters The figure reveals a certain number of parameters common to several columns (see line connectors), which create circular interactions between the various subsets of parameters. These interactions are linked by complex functions, which make a purely mathematical resolution of the problem nearly impossible. The resolution of the problem requires the definition of a hierarchy between the various parameters, followed by taking into account assumptions for the parameters of higher hierarchy. This hierarchy differs from one project to another, such as for example:


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For a short bored tunnel or a medium-length bored tunnel with one-way traffic, the most probable ventilation system is "longitudinal ventilation". The jet fans fixed in the crown have indeed usually a very low impact on the dimension of the cross-section. This one could thus be dimensioned initially before designing the ventilation, but by taking into account the other determining parameters. The impact of the ventilation on the cross-section will then be checked afterwards, Conversely, if the tunnel is very long or the cross-section is rectangular (cut and cover), the ventilation system and its components (section, number and nature of the possible air ducts dimension of the jet fans if required - etc.) have an essential impact on the cross-section size. The ventilation system will have to be pre-dimensioned at the beginning of the analysis by making preliminary assumptions of the dimension of the cross section. The geometry of the cross-section will then be checked.

The process of resolution is then iterative and based on a first set of assumptions, as the previous examples show. This process requires a large transverse multi-technical experience of the engineers, making it possible to take into account the relevant parameters for the project, to better target the successive iterations, and to guarantee the best optimisation of the project, with the required level of service and safety.

1.1.3. Subset "Ventilation" Table 1.1-4 below gives an example of the principal parameters concerning the aspects relating to ventilation. This table is not exhaustive. As for "civil engineering", the interactions between parameters are numerous. They also are subject to circular relations. The process to solve the problems is similar to the one outlined above for "civil engineering".


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Table 1.1-4 : Main parameters influencing ventilation

1.1.4. Subset "Operation equipment" They do not constitute fundamental parameters for the definition of the functional section, with the exception of: 

box-outs and sleeves for the passage of cables, pipes for water supply to the fire fighting system,


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signalling, signage for information, safety or police instructions. Signalling may have sometimes (rectangular cut and cover) a very important impact on the geometry (distance between roadway and soffit with a possible impact on the vertical alignment and the tunnel length). This may eventually require a more global optimisation, which may concern the position and/or the design of the interchanges outside the tunnel close to the portals.

"Operation equipment" constitutes on the other hand essential parameters for the dimensioning of the technical buildings at the portals, of underground M&E sub-stations, and of all underground technical spaces, or various provisions, recesses and niches. They often require particular arrangements concerning temperature, air conditioning, and air quality. They also are important parameters in terms of cost: construction, operation and maintenance. "Operation equipment" constitutes essential parameters regarding tunnel safety. It must be designed, built and maintained in this objective: 

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availability and reliability, in particular power supply and distribution, as well as all the communication networks, protection against fire of all equipment, in particular of the main power supply cables and the cables of the transmission networks, hardiness of the equipment and its components in order to guarantee its life-span, reliability and optimisation of costs: operation and maintenance, to facilitate maintenance interventions, their low impact on the traffic conditions, as well as on the safety of the maintenance teams and the users, which requires particular arrangements concerning the design and the accessibility of these facilities, integration of the procedures for operation, and the emergency response plan in the design of the supervision system (SCADA), the ergonomics of the man/machine interfaces, and assistance to the operator in particular during an incident.

1.1.5. Subset "Safety" 1.1.5.1. Concept "Safety" The conditions of safety in a tunnel result from many factors as presented in chapter 2 of this Manual.It is necessary to take into account all the aspects of the system formed by the infrastructure itself to ensure safety as well as its operation, interventions, vehicles and users (Fig. 1.1-5). Infrastructure is an essential parameter of construction cost. However, one can invest highly in infrastructure without improving conditions of safety if essential provisions are not considered in parallel concerning:    

Fig. 1.1-5 : Factors affecting safety

organisation, human and material means, the procedures of operation and intervention, training of operating staff, the emergency services' equipment with efficient material and training of their staff, communication with users.

1.1.5.2. How do these parameters affect a tunnel project? These parameters relating to safety may affect in a more or less important way a tunnel project. The tables below give some examples. Note: The four tables below refer to the four principal fields represented in Fig. 1.1-5. 

Column 1 indicates the principal infrastructure or actions concerned,


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Columns 2 and 3 indicate the degree of influence on the tunnel project (civil engineering ventilation - operating and safety equipment):   

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Green: important or major impact Yellow: medium impact, Red: no impact.

Column 4 specifies the main reasons or causes of influence.

Fig. 1.1-6 : Main impacts on the project due to infrastructure

Fig. 1.1-7 : Main impacts on the project due to intervention conditions and the organisation of the operation

Fig. 1.1-8 : Main impacts on the project due to vehicles

Fig. 1.1-9 : Main impacts on the project due to the tunnel users

1.1.6. Synthesis A tunnel is a "complex system" which means in particular that: 

approaching the design of a tunnel from the point of view of only the alignment, the geology or the civil engineering, leads to serious design deficiencies, which are likely to make the tunnel less safe (possibly even dangerous) and difficult to operate (perhaps impossible to be operated under reasonable conditions).


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in the same way, to approach the design of a tunnel from the point of view of only the operating equipment without integrating an upstream analysis of risks and safety, intervention and operation, will also lead to deficiencies that will very quickly appear as soon as the tunnel is open to traffic, not taking into account, from the preliminary design stage, all the objectives and constraints relating to the operation and to the maintenance, will inevitably lead to increased operational costs and to reduced overall reliability.

Partial treatment of problems is unfortunately still rather frequent, due to lack of sufficient "tunnel culture" of the various actors involved in the design. Control of this complex system is difficult but essential in order to:  

find the appropriate solution to each problem, ensure the users have an essential level of safety, and to offer them a service of quality and good comfort.

In a parallel way the control of this complex system very often contributes to the technical and economical optimisation of the project, by a clear and early definition of the functions to be ensured and by using a value engineering process. Taking into account, from the start of the project, the major issues relative to:    

horizontal and vertical alignments, geology, civil engineering construction provisions and methods, ventilation, safety (by a preliminary analysis of risks and danger and a preliminary emergency plan), operation and maintenance conditions,

constitutes an effective approach to solving this complex equation.


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1.2. General design of the tunnel (new tunnel) Section 1.2 relates to the design of new tunnels. The design concerning the refurbishment and the safety upgrading of tunnels under operation is presented in Section 1.3.

1.2.1 Horizontal and vertical alignment The design of the horizontal and vertical alignment of a road or highway section, which includes a tunnel, constitutes a major and fundamental first stage in the creation of a new tunnel, to which the necessary attention is seldom given. The consideration of the "complex system" which constitutes a tunnel has to start at the early stage of the design of the general alignment, which is seldom the case. It is however at this stage that technical and financial optimisations are the most important. It is essential to mobilise from the earliest stage of the design a multidisciplinary team made up of very experienced specialists and designers, who will be able to identify all the project's potential problems, despite inevitably incomplete preliminary information. This team will be able to make good and reliable decisions for the major choices, and then consolidate these elements progressively taking into account the availability of additional information. The objective of this section is not to define the rules regarding tunnel layout design (several countries' design handbooks are referred to in Section 1.6) but essentially to sensitise the owners and the designers to the necessity of a global and multicultural approach, from the early stages of the design, and to the importance of essential experience that is paramount to the success of the project.

1.2.1.1 Countries without "tunnel culture" In these countries owners and designers have a certain apprehension about tunnels. They very often prefer "acrobatic road layouts" passing along ridges, with steep gradients, huge retaining walls or very long viaducts, and sometimes tremendous consolidation works (which are very expensive and not always effective over a long period of time), in order to cross zones with active landslides. Numerous examples of projects including tunnels and alignment variations designed with a global “system” approach demonstrate, in comparison with approaches refusing systematically the construction of tunnels:  

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construction cost savings may reach between 10% and 25% in areas with mountainous conditions, important savings of operation and maintenance costs can be achieved. The reliability of the route can be improved, in particular in zones of instability or active landslides, or subject to severe climatic conditions, environmental impact is significantly reduced, the level of service for the users is improved, and the operating conditions, in particular in winter (in countries subject to snowfall) are made reliable by the reduction of the gradients required by passages along ridges.

The assistance of an external assessor makes it possible to mitigate the insufficiency or the lack of "tunnel culture", and to improve the project significantly.

1.2.1.2 Countries having a tradition of construction and operation of tunnels The concept of "complex system" is seldom integrated upstream, to the detriment of the global optimisation of the project. Too often the "geometry" of the new infrastructure is fixed by layout specialists without any integration of the whole of the constraints and tunnel components. It is however essential to take into account from this stage all the parameters and interfaces described in paragraph 1.1 above, and in particular:

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the general geology and hydrogeology of the area (with the available level of knowledge) as well as preliminary appreciation of the geological difficulties and the potential risks concerning the methods, costs and construction duration, the potential geomechanical, hydro-geological, hydrographical conditions at the tunnel portals and along the accesses, the risks and hazards related to winter conditions for countries subjected to noteworthy snowfall, in particular: - the risks of avalanche or formation of snow-drifts and the possibilities of protecting the access roads and the portals against these risks, - the maintenance conditions of access roads in case of significant snowfalls to guarantee the reliability of the route. This provision may condition the altitude of the tunnel portals, the maximum slopes of the access roads, and if necessary the place available to arrange surfaces for chaining and unchaining in the vicinity of the portals, the environmental conditions at the tunnel portals and on the access roads. The impact can be significant in urban environments (in particular because of the noise and the discharge of polluted air), as well as for interurban tunnels, the gradient of the approach ramps: - the least expensive tunnel is not always the shortest tunnel, - the suppression of a special lane for slow vehicles is difficult to manage in the vicinity of a tunnel portal, and keeping such a lane in a tunnel is generally very expensive, - the gradient of the access roads can have a very strong impact on the capacity of the route in terms of traffic volume and winter reliability. the possibility of incorporating adits as lateral accesses (ventilation - evacuation and safety reduction of the construction works schedule), or as vertical or inclined shafts (ventilation evacuation and safety), - these particular access points, their impact on the surface (in particular in urban environments: available space - sensitivity to the discharge of polluted air - etc), their year-round accessibility (e.g., exposure to avalanches) may constitute important constraints for the design of the horizontal and vertical alignment. Conversely they very often contribute to the optimisation of the construction and operation costs, - these particular access points may have a major impact on the construction and operation costs, and on the size of the cross section (potential optimisation of the ventilation and the evacuation facilities), the methods of construction which may have a major impact on the design of the horizontal and vertical alignment, for example: - crossing under a river with a bored tunnel constitutes an essentially different project to that of a solution by immersed prefabricated boxes, - interfaces with a viaduct at the tunnel portal, - the imposed construction deadline may have a direct impact on the layout, in particular to allow driving from both tunnel portals as well as intermediate drives, using adits, the geometrical characteristics of the layout and the longitudinal profile of the tunnel for which it is also necessary to integrate the following elements: - limitation of gradients, which have a major impact on the sizing of the ventilation system and on the reduction of the traffic volume capacity of the tunnel, - the hydraulic conditions of underground drainage during the construction and the operation period, which affect the vertical alignment, - reduced lateral clearance (construction of additional widths is very expensive) which require particular analysis of the visibility conditions and particular vigilance in the choice of the radii of the curves for the horizontal alignment, - the best choice of the radii in order to avoid alternating cross-fall slopes, and their major impact on water collecting and drainage systems from the carriageways, interfaces with sleeves for the


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installation of cables, water pipes for fire fighting, which can even lead to an increase in the dimension of the cross section, 

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all usual constraints related to the occupation of the underground space, in particular in urban environments: subways - car parks - foundations - structures sensitive to settlements, construction and operation costs: - the least expensive tunnel is not necessarily the shortest one, - an additional investment in civil engineering can be overall more economic over the tunnel lifetime if it enables a reduction of the costs for construction, operation, maintenance and heavy repairs (in particular ventilation), or if it makes it possible to postpone for several years the date of traffic capacity saturation (impact of the gradient in the tunnel and on the accesses), the coordination between the horizontal and the vertical alignments must be carefully studied in a tunnel in order to support the level of comfort and safety of the users. The visual effect of the changes of slopes in the vertical alignment, in particular in high points, is highlighted by the limited visual field of the tunnel and by the lighting, the conditions of operating with uni- or bidirectional traffic have to be taken into account in the design of the layout, in particular: - the usual conditions of visibility and legibility, - the possibility of arranging lateral accesses (adits) or vertical accesses (shafts), in particular for: optimisation of ventilation and the cross-section, improvement of safety (evacuation of the users and access of the emergency teams by avoiding the construction of an expensive parallel gallery), the layout in the vicinity of the portals: - the tunnel portals constitute singular points of transition, and it is necessary to take into account human behaviour and the physiological conditions. It is essential to preserve a geometrical continuity to make it possible for the user to preserve his instinctive trajectory, - a rectilinear tunnel is not desirable, in particular along the approach of the exit portal. It may be necessary to reinforce the exit lighting over a long distance, underground junctions at or very close to the tunnel portals: - interchanges inside a tunnel or outside in the immediate vicinity of the portals are to be avoided, - if they are unavoidable, a very detailed analysis must be made to determine all the constraints and particular consequences to be taken into account (layout - cross-section - exit or merging lanes - risk of backward traffic flow - evacuation - ventilation - lighting - etc) to ensure safety in all circumstances.

1.2.2 The functional transverse profile 1.2.2.1 The issues The functional transverse profile constitutes the second major stage of the design of a tunnel after selecting the alignment. As for the first stage, the "complex system" approach must be taken into account in a very attentive way, as upstream as possible with an experienced multidisciplinary team. All of the parameters and interfaces described in Paragraph 1.1 must be considered. This second stage (functional transverse profile) is not independent of the first stage (alignment), and it must obviously take into account the resulting provisions. The two stages are interdependent and very closely linked together. Moreover, as mentioned in paragraph 1.1.2.2 above, the process of the first two stages is iterative and interactive. There is no direct mathematical approach to bring a single response to the "complex system" analysis. There is also no uniqueness of answer but a very limited number of good answers and a great number of bad answers. The experience of the multidisciplinary team is essential for a good solution to be identified quickly.


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The examples quoted in paragraph 1.2.1 above illustrate that the provisions of the "functional transverse profile" can have a major impact on the design of the horizontal and vertical alignments. Experience shows that the analysis of the "functional transverse profile" is very often incomplete and limited to the sole provisions of civil engineering, which leads inevitably to: in the best case, a project that is not optimised from the functional, operational and financial points of view. Experience shows that potential optimisations can reach in exceptional cases 20% of the construction costs, in the most frequent case, an inadequate consideration of the functions, their constraints and their impacts on the project. These functions will have to be integrated in the following stages of the project by implementing late and often very expensive solutions, in the worst case, fundamental design errors with an irremediable and permanent impact on the tunnel, on its conditions of operation and safety, as well as on its construction and operation costs. 

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1.2.2.2 Principal provisions The major parameters of the "functional transverse profile" are as follows: 

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Traffic volume - nature of the traffic - operation organisation - urban or non-urban tunnel, in order to determine: - the number and width of the lanes, according to the traffic and the type of vehicles admitted to the tunnel, - the headroom (according to the type of vehicle), - the hard shoulder, emergency stopping lane or lay-by, according to the volume of traffic, the mode of operation, i.e. uni- or bidirectional, the statistical rate of breakdowns, - a possible central separator and its width in the event of bidirectional operation, Ventilation has a major impact which depends on: - the selected system of ventilation, itself depending on many other parameters (see Paragraph 8.5), - the space required for the ventilation ducts, for the installation of axial fans, jet fans, secondary ducts, and all the other ventilation equipment, Evacuation of the users and the access of the emergency and rescue teams which depend on the numerous factors detailed in Chapter 7, The length and the gradient of the tunnel. These parameters intervene in an indirect way through the ventilation, the concepts of access and safety, The networks and equipment for operation are also very often determining factors in the dimensioning of the functional cross section, taking into account their number, the space they require, the essential protection associated with them to guarantee the operational safety of the tunnel, and the relatively limited space under the walkways and hard shoulders to locate them. The following networks are in particular concerned, which have a dimensional impact: - separated or combined sewer system(s) - collection of polluted liquids from the roadways and associated siphons. The absence of variation in the crossfall, associated with the conditions of the alignment (see § 1.2.1.2) allow a simplification and an optimisation of the functional transversal profile, - water supply network for the fire fighting system, fire hydrants, and if necessary their protection against freezing, - all networks of cables of high and medium voltage, as well as low voltage currents. It is essential to take into account on the one hand, the cables necessary at the time of the tunnel opening and their protection against fire, as well as the provisions allowing their partial or total replacement, and on the other hand the provisionsfor the inevitable addition of other networks throughout the tunnel's life, - the particular needs in the short or medium term for external networks likely to pass through the tunnel, - all interactions between networks and needs (technical or legal) for spacing between some networks,


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- all of the signalling for operation: signalling and signage - lane signals - panels with variable messages - regulation indications - safety indications - directional indications, 

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Localised functional interfaces: underground sub-stations - underground ventilation plant - safety recesses - shelters - etc. It is essential to take into account the provisions for operation and the maintenance, and in particular the construction of lay-bys for maintenance interventions and the safety of the operating teams, Construction methods and geological conditions have an impact on the functional transverse section (independently of the dimensioning of the civil engineering structures), for example: - the underwater crossing mentioned in section 1.2.1.2 above. The solution with immersed precast boxes enables a very different design and arrangement of the ventilation system, the evacuation galleries or the access of the emergency teams, in comparison with the arrangement for the same equipment in the case of a bored tunnel, - a tunnel bored with a TBM (tunnel boring machine) makes surfaces available under the roadway which can be used for example for ventilation, for the users' evacuation, or for the access of the emergency services. This can allow optimisations (removal of connection galleries or a parallel gallery) which can be financially very important if the tunnel is located under groundwater level in permeable materials.

1.2.3 Safety and Operation 1.2.3.1 General provisions PIARC's recommendations are numerous in the fields of safety and operation for the finalisation of safety studies, the organisation of operation and emergencies, as well as the provisions for operation. The reader is invited to refer to theme : see Chapter 2 "Safety" and Chapter 3 "Human factors regarding tunnel safety"). This present chapter primarily treats safety and operation interfaces within the "complex system". The tables of section 1.1.5.2 above indicate the degree of interdependence of each parameter compared to the various subsets of the project. A certain number of parameters have a major impact from the upstream stages of the project onward. They must be analysed from the first phases of the design and deal in particular with: volume of traffic - nature of the traffic (urban, non urban) - nature of vehicles (possibly tunnel dedicated to one category of vehicles) - transport or not of dangerous goods, evacuation of the users and access of the emergency teams, ventilation, communication with the users - supervision system. 

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These major parameters for the design of the tunnel are also the essential factors of the "hazard analysis", and drafts of the "intervention plan of the emergency teams". This is why we consider that it is essential that a "preliminary risk analysis", associated with a preliminary analysis of an "emergency response plan" should be carried out in the initial stages of the preliminary design. This analysis makes it possible to better describe the specific features of the tunnel and the functional and safety specifications which it must satisfy. It also contributes to a value engineering analysis, to a better design and to the technical and financial improvement and optimisation. These parameters and their impacts are detailed in the following paragraphs

1.2.3.2 Parameters relating to the traffic and its nature These parameters have an impact mainly on the functional cross-sectional profile (See 1.2.2), and through it a partial impact on the layout: the volume of traffic affects the number of lanes, ventilation and evacuation. It also affects the impact of breakdown vehicles and their management when stopped: requirement for a lateral stopping lane or not, for lay-bys, and organisation of particular provisions for repair service, 


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the nature of the traffic, the type of vehicles and their distribution affect the evacuation concept (cross-passages, evacuation galleries, their dimensioning, their spacing) according to the volume of people to be evacuated, tunnels dedicated to particular categories of vehicle relate to the width of the lanes, headroom and ventilation, the passage or not of dangerous goods has an important impact on the ventilation system, the "functional cross-section", fluid collection and dewatering measures, diversion routes, the environment of the tunnel portals or ventilation stacks, the protection of the structures against the consequences of a major fire, as well as on evacuation and the organisation of the emergency services and the provision of the fire brigade in specific means and material.

1.2.3.3 Evacuation of the users - access of the emergency teams This is a fundamental parameter concerning the functional provisions and the general design. This parameter also often affects the alignment (direct exits to outside) and construction provisions: cross passages - under gallery - parallel gallery - shelters or temporary refuges connected to a gallery. Its analysis requires an integrated approach with the ventilation design (in particular the ventilation in case of fire), volume of traffic, risk analysis, drafting of the emergency response plan (in particular investigation of the scenarios ventilation / intervention) and construction methods. It is necessary from a functional point of view to define the routes, their geometrical characteristics and spacing in order to ensure the flow of able-bodied and disabled people. It is essential to insure the homogeneity, the legibility and the welcoming and calming character of these facilities. They are used by people in situations of stress (accident - fire), at the self-rescue stage (before the arrival of the emergency services). Their use has to offer a natural, simple, efficient and calming character in order to avoid the transformation of the state of stress into a state of panic.

1.2.3.4 Ventilation Ventilation facilities designed as a pure "longitudinal ventilation" system have little impact on the "functional cross section" or on the "alignment". This is not the case for "longitudinal ventilation" facilities equipped with a smoke extraction duct, or for "transverse ventilation" systems, "semi-transverse" or "semi-longitudinal" systems, "mixed" systems, or for ventilation systems including shafts or intermediate galleries permitting to draw or to discharge air outside other than at the tunnel portals. All these facilities have a very important impact on the "functional cross section", the "alignment" and all the additional underground structures. The ventilation facilities of the traffic space are essentially designed in order to : provide healthy conditions inside the tunnel by the dilution of air pollution in order to keep the concentrations to a level lower than those required by the recommendations of national regulations, ensure the safety of the users in case of fire inside the tunnel, until their evacuation outside of the traffic space, by providing efficient smoke extraction, 

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The ventilation facilities may also provide additional functions: limitation of air pollution at the tunnel portals, by improved dispersal of the polluted air, or by cleaning the air prior to its discharge outside the tunnel, underground plants for cleaning the polluted air in order to reuse it within the tunnel. These facilities exist in urban tunnels or in very long non-urban tunnels. They are complex and expensive technologies, requiring a lot of space and considerable maintenance, in case of fire, to contribute to limiting the temperature inside the tunnel in order to reduce the deterioration of the structure by thermal effects. 

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the technical rooms or plants situated inside the tunnel or outside near the tunnel portals that may require air renewal, or management and control of the temperature level (air heating or conditioning according to the geographical conditions).

The ventilation facilities have to be designed in order to be able to: 

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adapt in a dynamic and fast way to the numerous conditions and capacities in which they are operated in order to face : - climatic constraints, in particular significant and fluctuating differentials of pressure between the portals for long tunnels in mountainous areas, - variable operating rates for smoke management in case of fire, according in particular to the development of the fire, then its regression, as well as throughout the fire period in order to be suited to the evolution of the fire fighting strategies at each stage of evacuation, of fire fighting, of preservation of the structures, etc. present enough development capacity in order to be able to adapt throughout the tunnel's life to the evolution of the traffic (volume - nature), lowering of the admissible pollution levels and various conditions of operation.

1.2.3.5 - Communication with the users - supervision Communication with users has an important impact on the "functional transverse profile" through signalling. The other major impacts do not relate to the whole of the "complex system". They relate to the subsystem concerning the operating equipment, in particular remote monitoring, detection, communications, traffic management, control and supervision, as well as the organisation of evacuation.

1.2.3.6 - Particular requirements for operation The operation of a tunnel and the intervention of the maintenance teams may require particular arrangements in order to enable interventions under full safety conditions, and to reduce restrictions to the traffic. These arrangements concern for example the provision of lay-bys in front of the underground facilities requiring regular maintenance interventions, accessibility to materials for their replacement and maintenance (in particular heavy or cumbersome material).

1.2.4 The operating equipment The objective of this section is not to describe in detail operation facilities and equipment, their function or their design. These elements are defined in the recommendations of the current "Road Tunnels Manual", as well as in the handbooks or national recommendations listed in section 1.6 below. The objective is to draw the attention of owners and designers to the particular issues peculiar to the equipment and the facilities of tunnel operation.

1.2.4.1 Strategic choices The operating equipment must allow the tunnel to fill its function, which is to ensure the passage of traffic, and to satisfy the double mission of providing for the users a good level of comfort and safety when crossing the tunnel. The operation facilities must be suited to the function of the tunnel, its geographical location, its intrinsic features, the nature of the traffic, the infrastructures downstream and upstream of the tunnel, the major issues relating to safety and to emergency organisation, as well as the regulation and the cultural and socioeconomic environment of the country in which the tunnel is situated. A plethora of operation facilities does not automatically contribute to the improvement of the level of service, comfort and safety of a tunnel. It requires increased maintenance and human intervention, which, if not implemented, may lead to a reduction in the reliability of the tunnel and its level of safety. The


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juxtaposition or the abuse of gadgets is also useless. The facilities must be suited, complementary, sometimes redundant (for the essential functions of safety), and have to form a coherent whole. The facilities of operation are "living": 

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They require a rigorous care and maintenance regime, recurrent and suited to their level of technology. This maintenance has a cost and requires skilled human resources, as well as recurrent financial investment throughout the tunnel's life. Lack of maintenance (or insufficient maintenance) leads to major dysfunctions, to the failing of the facilities, and as a consequence to the calling into question of the tunnel's function and the users' safety. Maintenance of the facilities under traffic conditions is often difficult and very restricted. Arrangements must be considered from the design of the facilities. For this reason the "architecture" of the systems, their design and their installation have to be thought out in order to limit the impact of the dysfunctions on the availability and the safety of the tunnel, as well as the impact of the maintenance interventions or the renovation of the facilities, Their "life span" is variable: about ten to thirty years according to their nature, their hardiness, the conditions to which they are exposed, as well as the organisation and the quality of the maintenance. They must therefore be replaced regularly, which requires adequate financing, Technological evolution often makes essential the replacement of facilities that include advanced technologies, because of technological obsolescence and the impossibility of obtaining spare parts, The facilities must show evidence of adaptability to take into account the evolution of the tunnel and its environment.

All these considerations lead to strategic choices of which the main ones are: 

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To define the necessary facilities according to the real needs of the tunnel, without yielding to the temptation of accumulating gadgets. Risk analysis combined with value engineering is a powerful tool allowing the rationality of the choice of the necessary facilities. This approach also allows to better master the complexity of the systems, that is often a source of delays, cost over-runs and major dysfunctions if this complexity has not been managed by a rigorous and competent organisation, To give priority to the quality and the hardiness of the equipment in order to reduce the need and frequency of maintenance and the difficulties of intervention under traffic conditions. This can result in a higher investment cost but is compensated very extensively during the operation period, To verify the quality and the performance of the facilities at each stage of the design, manufacture, factory acceptance tests, installation on site and then site acceptance tests. Experience shows that numerous facilities are deficient and do not satisfy the objectives because of lack of rigorous organisation and efficient controls, To choose technologies suitable to the climatic and environmental conditions, which the facilities will have to face, as well as to the socio-cultural conditions (deficiency of the maintenance concept in some countries), and to technological and technical conditions, as well as to the organisation of the services, To take into account, from the design of the facilities and the choice of the equipment, the operation costs and in particular energy costs. These costs are recurrent throughout the tunnel's life. Ventilation and lighting facilities are in general the highest consumers of energy. Particular attention must be drawn to this aspect from the preliminary design stages, To take into account from the preliminary stages of design and financing analysis: -the necessity to implement, to organise, to learn and to train teams dedicated to operation and intervention on the one hand, and on the other hand to cleaning and maintenance, -the constraints of intervention under traffic conditions for maintenance,resulting operation, maintenance and refurbishment costs, To take into account in the general organisation and scheduling of a new tunnel project, the time required to recruit the teams and to train them, for tests, as well as the "dry run" of all the facilities and systems (period of 2 to 3 months), for practices and manoeuvres on site with all the external


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intervening parties (in particular emergency services - fire brigade) in order to familiarise them with the particularities of the tunnel.

1.2.4.2 - Key recommendations concerning the main facilities 1.2.4.2.a Energy - sources of power - electric distribution For the tunnel equipment to function there must be a power sources. Large tunnels can require a power of several MW (megawatts), which may not always be available on site. Particular arrangements must be taken from the first stages of the design in order to strengthen and make more reliable the existing networks, or often to create new networks. The power supply is essential for the operation of the tunnel. It is also essential for its construction. The supply of electric energy and its distribution inside the tunnel must provide:   

the required capacity, a reliable supply, a reliable, redundant and protected energy distribution system: redundancy and interconnectionof the distribution networks - transformers in parallel - cables located inside sleeves and in manholes protected against the fire.

Every tunnel is specific and has to be subjected to a specific analysis according to its geographical position, the context of the existing electrical networks, the energy supply conditions (priority or not priority), the possibility of increasing or not the power and the reliability of the existing public networks, the risks peculiar to the tunnel, as well as the conditions of intervention of the emergency services. The facilities must be then designed consequently, and the operating procedures must be implemented according to the reliability of the system and the choices that have been taken during the design period. The objectives concerning safety, in case of a power supply cut are: 

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immediate emergency supply without interruption of all of the following safety equipment during a period of about half to one hour (according to the tunnel and the evacuation conditions) : - minimal lighting level - signalling - CCTV monitoring - telecommunications - data transmission and SCADA - sensors and various detectors (pollution - fire - incidents - etc.), - power supplies to safety niches, evacuation routes and shelters, - this function is usually ensured by UPS systems, or diesel generators immediately able to supply energy, varying from tunnel to tunnel, its urban or rural location and the risks incurred, additional objectives of MOC (Minimal Operation Conditions) can be set to assure the electrical supply of the following equipment, as long as specific procedures are implemented during the whole duration of the power cut. For example: emergency power supply of the ventilation system (by generators or a partial external supply) permitting the tackling of light vehicle fires, but not truck fires: the passage of trucks is then temporarily forbidden.

The arrangements usually implemented for the electrical power supply are as follows: 

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Emergency power supply from the public network: - 2 to possibly 3 supplies from the public network grid with connections to independent segments of the high voltage or middle voltage network. Automatic switching between "normal supply" and "emergency supply" inside the tunnel power substation with, if required, interruption of the power supply to some of the equipment, if the emergency external power supply is insufficient, - no diesel generators, - installation of a UPS emergency power supply. No external emergency power supply: - a single external power supply from the public network, - diesel generators able to provide a part of the power in case of interruption of the main external power supply, and setting up of MOC and particular operating procedures, - installation of a UPS emergency power supply.


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Full autonomy of the power supply - no external power supply available: - the public network is not able to provide the required power, or does not have the required reliability. The tunnel is then in complete autonomy. The energy is entirely provided by a set of diesel generators working simultaneously. An additional generator is installed as "back up" in case one of the generators should fail, - possible installation of a UPS emergency power supply, if the level of reliability of the generators is considered insufficient, or for safety reasons.

1.2.4.2.b Ventilation PIARC recommendations are numerous in this field and constitute the essential international references for the conception and the design of ventilation facilities.In addition to section 1.2.3.4 above, the reader should refer to Section 8.5. However, it must be remembered that even if the ventilation equipment constitutes one of the essential facilities in assuring the health, comfort and safety of the users in a tunnel, it is only one of the links of the system, in which the users, the operators and the emergency and rescue teams constitute the most important elements by their behaviour, their expertise and their capacity to act. The ventilation facilities alone cannot deal with all scenarios, nor satisfy all the functions that might be assumed, especially concerning air cleaning and the protection of the environment. The relevance of the choice of a ventilation system and its dimensioning requires lengthy experience, the understanding of the complex phenomena of fluid mechanics in an enclosed environment, associated with the successive stages of the development of a fire, the propagation, radiation and thermal exchanges, as well as the development and the propagation of toxic gases and smoke. The ventilation facilities are in general energy-consuming and particular attention must be paid to the optimisation of their dimensioning and their operation, by using for example expert systems. The ventilation facilities may be very complex, and their relevant management in case of fire may require the implementation of automated systems that allow to manage and master the situation more efficiently than an operator under stress. As indicated in section 1.2.3.4 above, the ventilation facilities must above all satisfy the requirements for health and hygiene during normal conditions of operation, and to the objectives of safety in case of fire. Hardiness, reliability, adaptability, longevity and optimisation of energy consumption constitute major quality criteria that the ventilation facilities must satisfy. 1.2.4.2.c Additional equipment to the ventilation facilities Two types of additional equipment for ventilation are often the subject of pressing demands from stakeholders, resident associations or lobbies:  

Air treatment or air cleaning facilities, Fixed fire suppression systems.

A. Air cleaning facilities. Section 5.1 deals with this question and the reader is invited to refer to it.

The implementation of air cleaning facilities is a recurrent demand of resident protection associations in urban areas. These facilities, usually installed underground, are very expensive to construct as well as to operate and maintain. They are also high consumers of energy. Results to date are far from convincing, due in particular to important emission reductions from the vehicles, and to the difficulty for these systems to clean the very low concentrations of pollutants that are in the tunnel, contained in large volumes of air. Consequently, many systems installed in the last ten years are no longer operational. The future of air cleaning facilities is very uncertain in countries where there is more coercive regulation, imposing more and more rigorous reductions of polluting emissions at the source. B. Fixed fire suppression system (FFSS). Section 8.7 deals with this issue, and the reader is invited to refer to it.


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The technologies are numerous and answer to varied criteria: fire fighting - containment of the fire reduction of thermal radiation and temperature for the users situated in the vicinity of the fire preservation of the tunnel structure against damage due to high temperature, etc. These systems, even though presenting positive aspects, also present negative aspects related in particular to the deterioration of the conditions of visibility if they are activated from the start of the fire. The use of an FFSS requires a coherent approach to all aspects of the users' safety, as well as to ventilation and evacuation strategy. The decision concerning the implementation or not of such systems is complex and has important consequences. It must be subject to a thorough reflection relating to the particular conditions of safety of the work concerned and to the added value obtained by the implementation of the system. It should not be taken under the influence of fashion or a lobby. The FFSS requires the implementation of important maintenance measures, the carrying out of regular and frequent tests, without which its reliability cannot be assured. 1.2.4.2.d Lighting The recommendations of the CIE (International Commission for Lighting) have been criticised by PIARC because of the high levels of lighting to which they often lead. The reader is invited to refer to the technical report published by the European Committee of Normalization that presents several methods including the CIE's. Lighting is a fundamental tool to ensure the comfort and safety of the users in a tunnel. The objectives of the lighting level must be adapted to the geographical location of the tunnel (urban or not), its features (short or very long), to the volume and nature of the traffic. Lighting equipment consumes a lot of power and developments are in progress to optimise their features and performance. 1.2.4.2.e Data transmission - Supervision - SCADA SCADA is the "nervous system" and the "brain" of the tunnel, permitting the compilation, transmission and treatment of information, and then the transmission of the equipment's operating instructions. This system requires a meticulous analysis according to the specific conditions inside the tunnel, its facilities, the organisation and the mode of operation, the context of risks in which the tunnel is placed, as well as the arrangements and procedures implemented for interventions. The organisation of the supervision and control centre has to be analysed very carefully, according to the specific context of the tunnel (or of the group of tunnels), the necessary human and material means, the missions to be assumed, the essential aid brought by the automatic devices or the expert systems to the operators in event of an incident, allowing the operators to reduce and simplify their tasks and to make them more efficient. The detailed design of these systems is long, delicate and requires a very rigorous methodology of developing, of controlling by successive stages (in particular during factory tests), of testing, of globally controlling after integration of all the systems on site. Experience shows that the numerous errors noted on these systems come from the following gaps: 

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badly defined specifications, insufficient functional analysis, or ignorance of operational conditions and procedures, late systems development, which does not allow the time necessary for detailed analyses, transverse integration, or to take into account the peculiar conditions of operation of the tunnel, lack of rigour in the development, testing, control and integration of all of the systems, lack of taking into account human behaviour and general ergonomics, lack of experience in tunnel operation, in the hierarchy of the decisions that are to be integrated and the logical sequences of these decisions in the event of a serious incident.

Section 8.2 of the manual sums up these different aspects.


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1.2.4.2.f Radio-communications - low voltage circuits These facilities include:  

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emergency phone network, radio network for the operation teams and the emergency services. Radio channels for tunnel users, through which it is possible to transmit information and instructions related to safety, numerous sensors destined for taking measurements and detection, CCTV network. an AID system (Automatic Incident Detection) is usually associated with a CCTV system. The AID system requires an increased number of cameras in order to make detection more reliable and more relevant.

1.2.4.2.g Signalling Signalling refers to Section 8.9. Even more than for the other facilities, an overabundance of signalling is detrimental to its relevance and objectives. The legibility, the consistency, the homogeneity and the hierarchy of signalling (priority to evacuation signalling and information for users) have to be a priority of the signalling design inside the tunnel and on its approaches. Fixed signage panels, traffic lanes signals, variable messages signals, traffic lights and stopping lights, signalling to emergency exits, the specific signalling of these exits, signalling of safety niches, physical devices for closing the lanes (removable barriers),horizontal markings and horizontal rumble strips are all part of the signalling devices. They assure a part of the communication with the users. 1.2.4.2.h Devices for fire fighting The devices for fire detection are either localised (detection of fire in the underground substations or the technical rooms), or linear (thermal sensing cable) inside the traffic space. There are various devices for fire fighting:   

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automatic facilities in the technical rooms and underground substations, powder extinguishers for use by drivers, facilities for firemen: water pipe and hydrants - foam pipe in some countries. The volume of the water tanks is variable. It depends on the local regulations and the particular conditions of the tunnel. Some tunnels have an FFSS (see § 1.2.4.2.c above).

1.2.4.2.i Miscellaneous equipment Other equipment may be installed according to the objectives and needs concerningsafety, comfort and protection of the structure. Some examples are:  

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luminous beacons inserted in the side walls or walkway kerbs, a hand rail or a "life-line" fixed on the side wall permitting the movement in safety of firemen in a smoke-filled atmosphere, painting of the side walls or the installation of prefabricated panels on the side walls, devices for the protection of the structures against damage resulting from a fire. Such protective arrangements have to be taken into account from the origin of the project. Thermal exchanges (with the concrete lining or with the ground) are indeed modified during a fire, as well as air characteristics, which must be designed for when dimensioning the ventilation facilities, management and treatment of water collected on the road pavement inside the tunnel before discharge outside in the natural environment, arrangements for the measurement of environmental conditions at the tunnel portals, associated with particular operational procedures if the limits defined by the regulations are exceeded.


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1.3. Renovation – upgrading of existing tunnels The upgrading (in particular for safety improvement) and refurbishment of existing tunnels in operation gives rise to specific problems of analysis and method. The degree of freedom is less than for new tunnels, because it is necessary to take into account the existing space and constraints. The technologies peculiar to each type of equipment and their integration are however identical. The renovation and upgrading of a tunnel under operation quite often result in an increase of the construction schedule and costs, in much lower safety conditions during the works, and with badly controlled impacts on the traffic volume and conditions. These disadvantages are often the result of an incomplete analysis of the existing situation, the real condition of the tunnel, its facilities and its environment, as well as of a lack of strategy and procedures that would mitigate the effects on the traffic. Section 2.8 proposes a methodology for the safety diagnosis of existing tunnels and the development of an upgrading programme. In addition, Section 4.9 presents specific issues related to works carried out on tunnels in operation. Their dispositions help mitigate the problems mentioned above. It however appears appropriate to draw the reader's attention to the key points of the following sections.

1.3.1. Diagnosis Detailed and rigorous diagnosis of a tunnel is an essential stage in the process of its upgrading or renovation. Unfortunately this stage is often neglected. The physical diagnosis of a tunnel requires: to establish in detail and to describe in a precise manner the functions and the geometry of the structure, to establish a detailed condition statement of the structure. To evaluate in particular fire resistance, uncertainties and potential risks, and to list the tests that would be needed in order to provide a solid basis for the detailed design, to list all existing equipment, their functions, their condition, their technology, their actual features (tests or measurements will be required) and the s tock of spare parts that might be available, to evaluate the remaining life span of the aforementioned equipment before their replacement, and to identify the availability or not of spare parts on the market (notably because of the technological obsolescence), to identify maintenance and inspection reports, equipment malfunctions and the rate of breakdowns. This physical diagnosis must be supplemented by a diagnosis concerning the organisation, maintenance and operation procedures, as well as by a specific diagnosis concerning all documents relating to the organisation of safety and rescue interventions. This stage of diagnosis may eventually lead to the setting up of actions for the training of the various intervention parties in order to improve the global conditions of safety of the tunnel in its initial state prior to renovation. 

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The diagnosis must be followed by a risk analysis of the tunnel based on its actual state. This analysis has a double objective: to assess if the tunnel can continue to be operated in its present state prior to renovation, or if it is necessary to take temporary transitional arrangements: restriction of access to some vehicles only strengthening of the arrangements for surveillance and intervention - additional equipment - etc., to constitute a referential of the existing state from the point of view of safety in order to refine the definition of the renovation programme. The diagnosis has to identify (without running the risk of late discoveries during the works period) if the existing facilities, supposedly in working condition, can be modified, be added to or integrated in the 

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future updated facilities (technological compatibility - performance in particular for data collection and transmission, automatic functioning devices and SCADA).

1.3.2. Renovation or upgrading programme The renovation or upgrading programme proceeds from two stages. 1.3.2.1. First stage: programme development

The development of the programme results from: the detailed diagnosis as described above, the risk analysis developed considering the initial state of the tunnel, the gaps noted concerning safety, the analysis of what it is possible to achieve in the existing spaces and their potential enlargements in order to enable the upgrading of the tunnel. Depending on the physical environment of the tunnel and the spaces available, the optimum upgrading programme for the infrastructure or equipment may not be feasible under acceptable conditions, and that it is necessary to define a more restricted programme. This restricted programme may require the implementation of mitigating measures ensuring that the required level of safety is achieved in a global sense, after completion of the works. 

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1.3.2.2. Second stage: validation of the programme

The validation of the programme requires: development of a risk analysis based of the final state of the tunnel after upgrading in order to test the new arrangements introduced by the programme. This analysis has to be established with the same methodology that the one used for the prior analysis based on the initial state. It also enables a search for optimisations, detailed examination of the feasibility of the works to be carried out for the improvement or the renovation under the requisite conditions of operation: for example, banning of tunnel closure or of temporary traffic restrictions. In case of incompatibility between the objectives of the programme and the works required for its application, iteration is necessary. This iteration may concern : - the programme itself, insofar as adaptation of the programme is compatible on the one hand with the safety objectives, and on the other hand with its implementation in the required conditions of operation, - the required conditions of operation that it may necessary to modify in order to be physically able to carry out the works resulting from the upgrading programme. The upgrading or improvement programme does not necessarily require physical works. It may only consist in a modification of the functions of the tunnel, or of the operating arrangements, for example: 

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modification of the category of the vehicles authorised to access the tunnel: no access to trucks – no access to vehicles carrying dangerous goods, setting up of specific procedures for traffic restriction: in a permanent way or only during peak traffic, tunnel operated initially in bi-directional traffic, transformed for the implementation of unidirectional traffic, modification of the means for supervision or intervention.

1.3.3. Design implementation and construction The stage of design implementation and construction involves translating the renovation or upgrading programme into technical and contractual specifications and implementing it. This stage requires a very detailed analysis of:


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the successive stages of construction, the content of each of these stages, the logical and priority sequences of the works, safety conditions inside the tunnel at each construction stage. This requires partial risk analyses and the implementation if necessary of mitigation arrangements: traffic regulation – traffic restrictions patrol – strengthening of the intervention means - etc. traffic conditions inside the tunnel and on its approaches, with partial and temporary restrictions according to the various stages of works (different arrangements for daytime and night-time, for normal periods and vacation periods), of the potential diversions, of the global impact on the traffic and safety conditions in the areas concerned by the works, the constraints and subjections, the partial and global contractual deadlines for the works, in order to be able on the one hand to define the contractual specifications for the contactor, and on the other hand to implement all necessary temporary arrangements, and to proceed to an information campaign for the users and residents.


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1.4. Stages of the "tunnel life" Arbitrarily the "tunnel life" may be broken down in several main stages w hose essential stakes are:

1.4.1. Design This is the most important stage of the life of a new tunnel. It is decisive in terms of construction and operation costs, safety, as well as management of the technical and financial risks. This stage requires a transverse integration of all interfaces of the “complex system" that constitutes a tunnel. This integration has to start from the earliest stage of the design (see paragraphs above). Experience testifies to the fact that this is unfortunately rarely the case and that often the design of a tunnel results from a succession of stages considered as independent. Albeit caricaturising, we can note that:  

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the function is not always clearly defined, the alignment is designed without any integration of the tunnel, of its constraints, or of the whole set of optimisation possibilities, the civil engineering “manages” with the set horizontal and vertical alignments, with all the consequences that can result concerning the construction costs and risks, the equipment, safety level and operation fit in somehow and not always harmoniously or optimally with the arrangements chosen during the previous stages.

1.4.2. Construction For what concerns Civil engineering , the most important aspect is the management of technical risks (in particular geological) and of all the resulting consequences concerning construction costs and duration.

Considerations relating to risk management for the construction have to be taken into account from the design. These considerations must be detailed and shared with the owner of the tunnel. Decisions concerning the risks must be developed and clearly documented. The decision to take some risks does not necessarily constitute a mistake and must not necessarily be forbidden, because as a result some imperatives may be met, for example concerning a tight schedule, which would be incompatible with the implementation of all the investigations that would be required to eliminate all uncertainties. However the decision to take a risk must result from a very detailed reflection concerning: 

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consequences that may result, which must be clearly identified, analysed and consigned: delays costs - human and environmental impacts – safety – schedule – etc., the real issues of this decision, its probability of success and its real interest.

Taking of a risk must not be the result of carelessness or incompetence on the behalf of the various parties. For what concerns Operational facilities, the reader’s attention is drawn to:  

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all aspects likely to optimise the life span of the equipment, its reliability and ease of maintenance, the need of rigorous process and continuous control of the functionality, performances and quality of the equipment throughout the manufacture of the components, their assembly, their installation on the site, then at the time of partial and global testing after integration, the added bonus to quality concerning the choice of the equipment and the contractor, even though the construction costs may be a somewhat higher. Possible savings due to reduced initial costs are often quickly compensated for by higher maintenance costs, difficulties of intervention under traffic, and the additional constraints that would be suffered by the users.

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1.4.3. Commissioning This stage of "tunnel life" is often under-estimated and taken into account tardily. It requires taking time that is not often granted, and leads to the commissioning of the tunnel under unsatisfactory conditions, or even under conditions that are highly exposed in terms of safety. This stage includes:  

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the organisation of the operation and maintenance, development and adjusting of all procedures of operation, maintenance, intervention and safety under the normal conditions of tunnel operation, as well as under MOC (Minimal Operation Conditions), recruitment and training of the staff, the “dry run" of all the facilities, that cannot take place before the equipment has been fully completed, tested and delivered (possibly with provisions requiring only minor corrective interventions), the practice, training and manoeuvres involving all the intervention teams and services before commissioning the tunnel.

1.4.4. Operation The main mission is to ensure:  

the management of all facilities, their maintenance, their restoration, the safety and the comfort of the users.

It is also necessary to be able to look at the situation objectively with a distance to the daily routines in order to: 

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establish feedback from experience, adapt the procedures, the conditions of intervention, the training and the manoeuvres for safety, optimise operation costs without damaging the level of service and safety, identify, analyse, plan and achieve heavy repairs, and renovation and upgrading works.

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1.5. Costs of construction, operation, upgrading - financial aspects 1.5.1. Foreword Tunnels are relatively expensive civil engineering structures with respect to their construction and operation. Particular attention must be paid from the beginning of the project in order to spot any possible technical and financial optimisations. It is recommended from the first stages of the design to implement a process including:  

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the detailed definition of the "function" of the tunnel, an iterative process of “value engineering analysis" achieved at all strategic stages of the project, to which must be integrated into the various stages of the risk analysis, detailed analysis and monitoring of the potential risks in the design and construction stages. These potential risks are related to: - technical uncertainties relating in particular to the complexity of the ground (geological and geotechnical uncertainties), - uncertainties of traffic volume forecasts, that constitute an important risk concerning earnings in the case of construction and financing by “concession", - uncertainties and risks concerning the financial environment, in particular changes in interest rates and conditions of financing and refinancing. This aspect constitutes an important risk in the case of construction and financing by "concession" or by PPP (Private Public Partnership) with a financial contribution.

This process will enable the optimisation of the project (construction and operation costs) and an improved management of the technical and financial risks, as well as the schedule.

1.5.2. Construction costs 1.5.2.1. Cost ratios per kilometre

The construction costs of tunnels are very variable and it is impossible to give representative ratios of costs per kilometre, because these ratios may vary in important proportions (average of 1 to 5) according in particular to: the geological conditions, difficulties concerning the access roads and the tunnel portals, the geographical location of the tunnel: urban or non-urban, the length of the tunnel: in particular the "weight of the ventilation facilities and safety arrangements is more significant for a long tunnel; on the other hand all the works concerning the access roads and portals have a more important impact for a short tunnel, the traffic volume which is a determining factor for the dimensioning of the number of lanes, as well as for the ventilation facilities, the nature of the traffic: in particular a tunnel used by vehicles carrying dangerous goods will require expensive arrangements for ventilation, safety and possibly the resistance of the structure to fire; conversely, a tunnel dedicated to the passage of only light vehicles may enable very important savings because of the possible reduction of the width of the lanes, headroom and reduced requirements for the ventilation facilities, the tunnel environment that may lead to expensive protection arrangements for the mitigation of its impact, arrangements taken for the management or the sharing of construction risks, the socioeconomic environment of the country in which the tunnel is to be constructed. The impact can reach about 20% of the costs. At most it is possible to indicate that the average cost of a usual tunnel, built under average geotechnical conditions is about ten times the cost of the equivalent infrastructure built in open air (outside of urban areas).    

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1.5.2.2. Breakdown of the construction costs

The construction cost of a tunnel may be broken down into three types of cost:  

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the cost of the civil engineering structures, the cost of the operation facilities, including the supervision centre and the energy supply from public networks, various costs including in particular: owner’s costs for the development of the project – project management – design and site supervision – survey and ground investigations - environmental studies and mitigation measures – land acquisitions - various procedures - etc.

The two diagrams below show examples of the breakdown of construction costs, on the one hand for tunnels for which the conditions of the civil engineering works are not complex, and on the other hand for tunnels for which the conditions of the civil engineering works are less favourable. n o p a r t ic ic u l a r c o m p l e x it it y fo f o r c i vi v i l e n g i n e e r in in g

d i f fi f i c u l t c o n d i t io io n s f o r c i vi v i l e n g i n e e r in in g

breakdown of the construction costs

9%

15%

b r e a k d o w n o f t h e c o n s t r u c t io io n c o s t s

7%

15%

civil engineering

civil engineering

operation facilities

operation facilities

various

various

70% 84%

Fig. 1.5.1: Breakdown of construction costs Note: these two diagrams show how important the costs are of the civil works and illustrate the consequences of an almost doubling the costs of civil works (right-hand diagram).

1.5.3. Operation costs The operation costs of a tunnel may be broken down into three types of cost: 

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the operation costs as such, which essentially include staffing, energy, as well as the management and expendable equipment. These are recurrent costs; the recurrent yearly costs of maintenance; the costs of heavy repairs, as well as the replacement costs of the equipment according to its life span and its state during the tunnel life. These costs are not recurrent and depend on the equipment, its quality and the conditions of maintenance, from the tenth or twelfth year after the start of the operation period.

The two diagrams below represent examples of breakdown (with constant economic conditions) of the construction costs (civil works, operation facilities, various costs) and of the global operation costs (accumulated over a duration of thirty years after the start of the operation period). Note: these diagrams show how important the operation and maintenance costs are and how it is necessary to choose from the first stages of the tunnel design the arrangements that enable the optimisation of the recurrent operation and maintenance costs.


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no particular com plexity for civil engineering

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diffic ult cond itions for civil engineering

12%

8,5% 6,0%

9%

construction

construction

5,5% operation

operation 8%

m aintena nce m aintena nce h e a v y re re p a ir s h e a v y re re p a i rs rs 71% 80,0%

Fig. 1.5.2: Breakdown of the costs during a 30-year period

1.5.4. Costs of renovation and upgrading This chapter concerns the renovation or upgrading works that are required for “upgrading” to new regulations. The works concern the arrangements for evacuation, the resistance of the structure to fire, the operation and safety facilities, and all the requirements to satisfy the new safety regulations. It is not possible to give statistical prices due to the diversity of existing tunnels, their condition, their traffic and the more or less important requirements of new safety regulations that may vary from one country to another. The observations made in France for this nature of upgrading works for complying with the new regulations, which have been carried out since the year 2000, show a large variation of the corresponding budgets with wit h a range of costs between about ten t en million Euros and several hundred million Euros (there have been several upgrading programmes with a budget of more than 200 million Euros).

1.5.5. Aspects relating to financing Tunnels constitute costly infrastructure in terms of construction and operation, but this is offset by economic benefits including regional development, traffic fluidity, comfort, safety, reliable routes (mountain crossings) as well as protection of the environment. Financing of these works is ensured either by: 

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the “traditional mode”: financing and maintenance by a public authority, the financial resources coming then from public taxation or fuel taxes, a "concession" to a private or semi-public body, which is charged with the construction and the operation of the tunnel during a contractual period of time. This body is in charge of the financing (often partly by loan), which is offset by a toll paid by the users, that reimburses the costs of the construction and the operation, as well as the risks and the financial expenses. This type of "concession" can be granted by the financial involvement of the grantor or by particular guarantees (example: guarantee of a minimal traffic volume with the payment of a financial compensation if this minimal traffic volume is not reached), “mixed mode” of PPP (Public Private Partnership) or similar, that may concern: - only the construction or the construction and the operation, - construction under a “turnkey” scheme in the case of a “design and build” process, - partial or whole financing.

The present manual does not intend detailing these various modes of financing, or presenting their mechanisms, their advantages or disadvantages. However it is interesting to present some main guidelines found from experience, which give a preliminary illustration.


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a) Financing by a public authority

This mode of financing is employed widely. It allows the development of an infrastructure project, whose financing could not be achieved by a “concession” (by lack of sufficient income from toll collection), or when there is political will to avoid a toll. It requires however that the public authority has the financial capacity to ensure this financing, or that it has the capacity to borrow money and to support a debt. The financial resources essentially come from public taxation or fuel taxes and sometimes partially from toll collection. b) Financing by “concession” – tunnel part of a global infrastructure 

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The financing of a “non-freestanding tunnel” by a “concession” (with or without financial involvement of the grantor) is the general case for a tunnel that is part of a new interurban highway with toll collection. The costs (construction and operation) of the tunnel are shared out among the tunnel and the linear infrastructure above ground. Experience shows that the over-cost of the average toll ratio per kilometre is accepted by the users as long as the new infrastructure brings sufficient added value concerning time savings, better or more reliable service, comfort and safety. c) Financing by "concession" - isolated tunnel

Two main categories of isolated tunnels exist. Tunnels corresponding to a major improvement of the traffic conditions. This is in particular the case of urban tunnels aiming to alleviate traffic and to reduce travel times. Experience shows that financing by “concession” is only really foreseeable when the following conditions are met: - high traffic volumes, - country with high standard of living and revenues, enabling substantial toll rates, which are essential to ensure the financial balance, - Significant time gains for the users so that they will accept in return a relatively high toll rate, - duration of the concession of about fifty years at least. “Regional development” tunnels, intended to cross a major natural obstacle (chain of mountains estuary). These obstacles constitute an important handicap for trade. The initial traffic volume is usually relatively low. The new link with the tunnel will enable the growth of traffic, but such a development is often very difficult to predict in advance, and it constitutes an essential parameter of financial risk for the funding of the concession. Experience shows that financing by "concession" is then only realistic when the following conditions are met: - The natural obstacle is significant and the tunnel is sufficiently attractive (gain of time, level of service, delivered service, reliability of the link) in order to attract all existing traffic in spite of the toll, - Financial involvement of the grantor (possibly also the stakeholders), either with a financial contribution or direct involvement in the construction and the financing of a part of the works (for example construction of the access roads), - Guarantee of a minimal traffic volume by the grantor, with the payment of a contractual financial contribution if the minimal traffic volume is not reached, - Contractual arrangements for sharing major risks can put the financial model at risk if they over-run limits or conditions defined by the contract, - Very long concession duration: often 70 years or more, - Financial guarantee brought by the grantor, in order to enable the concession body to benefit from more favourable conditions of loans on the financial market, which may better ensure the feasibility of the financial plan. d) Financing by PPP or similar 

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The range of contents of a PPP mode is very wide, and it is difficult to establish guidelines because of the scope of possibilities. This mode of financing commits public authorities to financial contribution in the long term. Detailed analysis is necessary to evaluate the real advantage of this mode of financing compared to traditional financing. Indeed, this mode of financing very often contributes to increasing the global


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cost of the project (with equal functionality and quality) because of the compensation of the risk assumed by the developer. Public authorities have to carefully define the required functions of the tunnel, as well as objectives concerning quality, comfort, safety, level of service, life span, rate of availability, penalties etc. in order to prevent any ambiguity that may result in important misunderstandings and financial overruns in the development of the project.


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1.6. Regulations - Recommendations Countries that have many tunnels are endowed with regulations and have developed recommendations and guidelines for the design, construction, operation, maintenance, safety and the intervention of the rescue services. Concerning safety conditions in road tunnels, countries belonging to the European Union are subjected to Directive 2004/54/CE that prescribes a minimum level of arrangements to be implemented in order to ensure the safety of users in tunnels longer than 500 m that are part of the trans-European road network. A wider group of European countries are also bound by an international convention, The European Agreement concerning the International Carriage of Dangerous Goods by Road ( ADR ) and includes specific arrangements for tunnels. Every member country has transposed these European regulations to its own national legislation. Some member countries have implemented additional regulations that are more demanding than the one that results from the transposition of the European regulation. A list of the regulations and recommendations concerning the operation and the safety of road tunnels has been established in cooperation between the PIARC and the ITA Committee on Operational Safety of Underground Facilities (ITA-COSUF) of the international tunnelling and underground space association (ITA - AITES). This document can be consulted on the ITA-COSUF web site. This list is not exhaustive but presents an international panel of twenty-seven countries and three international organisations. Many countries do not have any regulations relating to tunnels and to tunnel safety, because they do not have road tunnels within their territory. It is recommended that these countries choose a complete and coherent package of the existing regulations of a country with lengthy experience in the field of tunnels, and not to multiply the origins of the documents by dipping into different sources. The recommendations of PIARC, as summarised in the present manual, as well as those of European directive 2004/54/CE also constitute international references that are being applied increasingly often.

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ROAD TUNNELS MANUAL

2. SAFETY

All rights reserved. © World Road Association (PIARC)


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2. Safety With the increasing number of tunnels under construction or in planning throughout the world, and the growing volume of traffic using existing tunnels, safety issues are becoming increasingly important. Incidents and accidents in road tunnels may be no more frequent than those on the open road, indeed road tunnels can provide a safer, more controlled driving environment for road users. However, the consequences of major incidents in the confined tunnel environment are potentially significantly more severe than on the open road and usually raise stronger reactions from the public. In a modern road tunnel, safety is assured by taking an integrated approach. Sets of well developed tools - like risk assessment, safety inspections and safety procedures - are available to help achieve the safety objectives from the initial planning and design stages of a new tunnel, through to the operation and upgrading of existing tunnels." An appropriate level of safety for tunnels that is comparable with that on the open road is achievable through a structured and integrated approach to the design and operation of tunnels that focuses on the prevention of serious incidents and the mitigation of consequences through the encouragement and facilitation of self rescue in the first instance and the subsequent effective intervention of the emergency services.

Accident in a bidirectional road tunnel (Video)

If you can not see this video, click here to load the video file.

Important lessons can be learned from the experience of past tunnel incidents, these are discussed in Section 2.3. Previous tunnel incidents have led to an increased international awareness and interest in tunnel safety impacts; indeed, following the report of the investigation after the Mont Blanc fire in 1999, a number of countries throughout the world initiated a review and update of national standards and guidelines for tunnel safety. The United Nations Economic Commission for Europe (UNECE) established a group of experts on road tunnel safety, with PIARC representation, which produced Recommendations in 2001 on all aspects of road tunnel safety. These recommendations have contributed to the development and update of international standards for tunnel safety. In Europe, the European Commission prepared a Directive on minimum safety requirements for road tunnels on the Trans European Road Network which entered into force in 2004.

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Action has also been taken in other parts of the world. In the USA, the national standard for fire safety in road tunnels ( NFPA 502) has undergone a periodic update, taking account of developments through research and learning from past tunnel incidents. The minimum requirements set out in the European Directive relate to tunnels that are on the Trans European Road Network. In countries throughout Europe and elsewhere, the regulations and requirements for tunnel safety may be more onerous than the requirements of the Directive. Such standards may be derived to account for the particular circumstances in the individual countries and to deal with tunnels that are not governed by the Directive, such as particular urban tunnels for example. The PIARC Technical Committee on Road Tunnel Operation has advanced the main issues regarding tunnel safety through the publication of a series of reports under dedicated Working Groups. In addition to its own activities and the legislative developments, a number of research projects and thematic networks, mainly in Europe, have contributed to the knowledge and understanding of the principles of tunnel safety and guided the tunnels community to the conclusion that there is a need for an integrated approach to road tunnel safety. These general principles are the subject of Section 2.1 of this Manual and the integrated approach is addressed in Section 2.2. More details on the international cooperative efforts aimed at better understanding and improving tunnel safety can be found in the following documents:  

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"Fire safety in tunnels" special issue Routes/Roads 324 (Oct. 2004) (8,65 MB) Initiatives since 2000 on road tunnel safety in Chapter 2 "Recent initiatives on road tunnel safety" of report 2007R07 Appendix A "International projects and networks" of report 2007R07

Further to these activities, PIARC supports the Committee on Operational Safety of Underground Facilities (ITA-COSUF) of the International Tunnel and Underground Space Association (ITA) as an international network for exchange of experience and promotion of safety. Key to the integrated approach to road tunnel safety is the establishment of safety level criteria, the analysis of safety and the evaluation of the balance between the costs and the benefits to achieve an acceptable level of safety. Fundamental to this is risk assessment, an essential tool for tunnel safety management, discussed in Section 2.4. Of particular importance and requiring particular attention in the analysis and evaluation of tunnel safety are fires in tunnels, discussed in Section 2.5 and the transport of dangerous goods, discussed in Section 2.6. To maximise the effectiveness of tunnel safety management, certain tools are needed to support strategy, to drive critical decisions and keep a constant and traceable view of all safety issues over a tunnel's lifetime. The three major tools regarding tunnel safety management are the Safety Documentation; the Collection and Analysis of Incident Data and Safety Inspections. These are described in some detail in Section 2.7. New requirements regarding safety, as well as increase in traffic, lead to upgrading existing tunnels. This raises specific problems which are examined in Section 2.8.

Contributors Input to this Chapter was coordinated by Working Group 2 of the C4 committee (2008-2011) in which: 

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Didier Lacroix (France), former president of the committee, supervised the writing of the chapter and reviewed the French text Gary Clark (UK), reviewed the English text and authored Sections 2.0, 2.1 and 2.2 Alejandro Sánchez Cubel (Spain), authored Sections 2.3 and 2.7 Blaž Luin (Slovenia) and Bernhard Kohl (Austria), authored Sections 2.4 and 2.6 Ignacio del Rey (Spain)and Fathi Tarada (UK) from WG4, authored Section 2.5 Jerome N´Kaoua (France) authored Section 2.8.

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2.1. General principles The management of safety has particular challenges in road tunnels where hazards of moving vehicles carrying loads are significant and the outcome of serious incidents may be significantly affected by human behaviour which can be difficult to predict ( Chapter 3). A'holistic' approach is necessary to take into account all aspects of the system consisting of the infrastructure, operation, emergency services, road users and vehicles. The first step in the assessment of requirements is to define the safety objectives. These are normally established at a national level in compliance with national laws, regulations and national standards with safety provisions being a function of the specific characteristics of the tunnel and the associated risk as defined through analysis and evaluation. Risk analysis and the evaluation of the acceptability of risk are addressed in Section 2.4 of this Manual. The fundamental principle to be followed is that in the event of an emergency in a tunnel, tunnel users will self-rescue. After the self-rescue phase of an emergency, the fire and rescue services will intervene to fight the fire and assist any remaining tunnel users that are unable to self-rescue. Safety objectives may be defined in various ways but the work of PIARC, the UNECE and the European Union agree on the broad definition of objectives as being:  

to prevent critical events, and to reduce the consequences of accidents.

Integrated safety for tunnels (Section 2.2) requires that attention be given to both of these two objectives. Such an approach may be presented as a "safety circle" from pro-action and prevention through to mitigation, intervention and evaluation; and back to pro-action, as shown in Fig. 2.1-1. More information on the objectives and general principles of safety is given in Chapter 3 "General principles" of report 2007R07. Actions aimed at meeting safety objectives and reducing risk may be classified in the following categories:     

Fig. 2.1-1: Safety circle

Tunnel user behaviour (Chapter 3) Operational and management measures (Chapter 4) Tunnel geometry (Chapter 6) Tunnel structural facilities (Chapter 7) Tunnel equipment (Chapter 8)

Information regarding each of the above topics is given in the relevant chapters of this manual as shown above. General information on the choice of safety measures can be found in the following documents:    



Chapter 2 "Safety concepts for tunnel fires" of report 05.16.B Technical report 05.13.B "Good Practice for the Operation and Maintenance of Road Tunnels" Chapter 4 "Safety practices" of report 2007R07 Technical report 2008R15 "Urban road tunnels - Recommendations to managers and operating bodies for design, management, operation and maintenance" Chapter 5 "Recommended additional measures to prevent escalation of critical traffic conditions in road tunnels" of report 2008R17

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The aim of safety planning and implementation is to achieve the right balance between the optimal safety level provision and the reasonable construction and operating costs. This may be achieved by taking an integrated approach to tunnel safety ( Section 2.2).

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2.2. Safety elements and integrated approach Safety is not the simple adoption of all possible safety measures but is the consequence of a balance between the forecast risk factors and the safety measures. With the establishment and development of international regulations, recommendations and guidelines, there is a need for a framework within which all aspects of tunnel safety are taken into account. Such a framework may contain the following principal elements: 















Safety level criteria (regulations & recommendations) Infrastructure and operational measures Socio-economic and cost-benefit criteria Safety assessment techniques (safety analysis and evaluation) Road tunnel usage Stage of tunnel life (planning, design, construction, commissioning, operation, refurbishment, upgrade) Operating experience Tunnel system condition

These safety elements are described in the Chapter 5 "Elements in an integrated approach" of report 2007R07.

An integrated approach is a framework to plan, design, construct and operate a new tunnel or an upgrade to an existing tunnel, fulfilling the required safety levels at each stage of the tunnel life. This should take place in accordance with a safety plan, following the right safety procedures.

Fig. 2.2-1: Integrated approach

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The opposite figure shows a schematic representation of a proposed integrated approach for the safety of new and in-service tunnels, comprising the elements listed above (figure from Chapter 6 "Conclusion" of report 2007R07.

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2.3. Experience from past tunnel incidents Information on incidents and accidents in tunnels, as well as lessons drawn, have been addressed by various reports of the PIARC Committee on Road Tunnels. Earlier reports present a statistical census of breakdowns, accidents and fires in selected tunnels, as well as the lessons to be drawn from such events for the geometric design of the tunnel, the design of the safety equipment and the operating guidelines - thus presenting a collection of data of vital importance to engineers and decision-makers involved in tunnel design :   



Technical report 05.04B "Road Safety in Tunnels" Chapter 2 "Fire risk and design fires" of report 05.05B : Chapter 2 "Information on previous large tunnel fires" of OECD/PIARC report on Transport of Dangerous Goods through Road Tunnels : Appendix 12.1 "Norwegian incident and accident statistics" of report 05.16B :

The incidents of Mont Blanc, Tauern and St. Gotthard (1999 and 2001) led to an increased awareness of the possible impact of accidents in tunnels. The likelihood of escalation of accidents into major events is low, however the consequences of such incidents can be severe in terms of victims, damage to the structure and impact on the transport economy.

Year

Tunnel

Lenght

Nbr Tubes

Casualties

1978

Velsen (The Netherlands)

770 m

2

5 fatalities and 5 injured

1979

Nihonzaka (Japan)

2 km

2


1980

Sakai (Japan)

460 m

2


1982

Caldecott (USA)

1,1 km

3


1983

Pecorile (near Genova, Italy)

660 m

2


1996

Isola delle Femmine (Italy)

148 m

2


1999

Mont-Blanc (France-Italy)

11,6 km

1

39 fatalities

1999

Tauern (Austria)

6,4 km

1


2001

Gleinalm (Austria)

8,3 km

1


2001

St. Gotthard (Switzerland)

16,9 km

1

11 fatalities

2006

Viamala Tunnel (Switzerland)

750 m

1


Table 2.3-1: Fires in road tunnels with 5 or more fatalities (due to fire or preceding accident) since 1950 A more complete table can be found on Table 2.1 "Serious fire accidents in road tunnels" of report 05.16.B. These catastrophes demonstrated the need for improving preparation for, as well as preventing and mitigating, tunnel accidents. This can be achieved by the provision of safe design criteria for new tunnels, as well as effective management and possible upgrading of in-service tunnels, and through improved information and better communications with tunnel users. Conclusions drawn from the enquiry following the Mont Blanc tunnel fire were that fatal consequences could be greatly reduced by: 

a more efficient organisation of operational and emergency services (harmonised, safer and more efficient emergency procedures, specifically for cross-border operation),

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more skilled personnel, more effective safety systems and greater awareness among users (car and truck drivers) on how to behave in emergency situations.

A detailed description of the Mont Blanc, Tauern and St. Gothard accidents including the original configuration of the tunnels, and a step-by-step guide to the accident, fire progression, and the behaviour of operators, emergency services and users, as well as the lessons to be drawn can be found in Chapter 3 "Lessons learned from recent fires" of report 05.16.B : . The lessons learnt are summarised in Table 3.5 of this report. Similar information is given in Routes/Roads 324 "A comparative analysis of the Mont-Blanc, Tauern and Gotthard tunnel fires" (Oct. 2004) on p 24. After the accident of march 24 th 1999, the Mont Blanc tunnel required significant renovation before it was able to be reopened to traffic. The ventilation system comprised a significant portion of the rehabilitation design work - a description of the dimensioning, automatic operation and full-scale fire tests can be found at Appendix 12.2 "The Mont Blanc Tunnel Renovation" of report 05.16.B . See Appendix 8 "Austrian statistical study of 2005: Comparative Analysis of Safety in Tunnels, during 1999-2003 period" of report 2009 R08 for a contrast of traffic safety of road tunnels on motorways and expressways compared with safety on other types of roads, and also traffic safety in tunnels carrying bi-directional traffic with safety in tunnels with uni-directional traffic.

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2.4. Risk assessment In the past, in many countries, the safety design of road tunnels to a great extent was based upon prescriptive regulations and guidelines. If the applicable prescriptions of relevant guidelines were fulfilled the tunnel was regarded as safe. However, this prescriptive approach has some shortcomings: 



Even if a tunnel fulfils all regulatory requirements it has a residual risk which is not obvious and not specifically addressed. A prescriptive approach defines a certain standard of tunnel equipment etc. but is not suited to take the specific conditions of an individual tunnel into account. Furthermore, in a major accident the situation is completely different to normal operation and a great range of different situations exceeding existing operational experience may occur.

Hence, in addition to the prescriptive approach, a risk-based approach - called risk assessment - can be used to address the specific features of a tunnel system (including vehicles, users, operation, emergency services and the infrastructure) and their impact on safety. Various types of risk can be addressed in a risk based approach, such as harm to a specific group of people (societal risk), or to an individual person (individual risk), loss of property, damage to the environment or to immaterial values. Commonly, risk analyses for road tunnels focus on the societal risk of tunnel users which can be expressed as the expected number of fatalities per year or as a curve in the FN diagram showing the relationship between frequency and consequences (in terms of number of fatalities) of possible tunnel accidents. Risk assessment is a systematic approach to analyse sequences and interrelations in potential incidents or accidents, thereby identifying weak points in the system and recognising possible improvement measures. Three steps characterise the risk assessment process: 



Risk analysis: Risk analysis is concerned with the fundamental question: "What might happen and what are the probabilities and consequences?". It involves the identification of hazards and the estimation of the probability and consequences of each hazard. Risk analysis can be carried out in a qualitative or in a quantitative way or as a combination of both. Two families of approaches are suitable for road tunnels: - a scenario-based approach, which analyses a defined set of relevant scenarios, with a separate analysis for each one, - a system-based approach, which investigates an overall system in an integrated process, including all relevant scenarios influencing the risk of the tunnel, thus producing risk indicators for the whole system. For system-based risk analyses, quantitative methods are common practice. Thus probabilities of accidents and their consequences for different damage indicators (e.g. in terms of fatalities, injuries, property damage, interruption of services) and the resulting risk are estimated quantitatively, taking due account of the relevant factors of the system and their interaction. Risk evaluation: Risk evaluation is directed towards the question of acceptability and the explicit discussion of safety criteria. In other words risk evaluation has to give an answer to the question "Is the estimated risk acceptable?" For a systematic risk evaluation safety criteria have to be defined and determination made of whether a given risk level is acceptable or not. Acceptance criteria must be chosen in accordance with the type of risk analysis performed. For instance, scenario-related criteria can be set to evaluate the results of a scenario-based risk analysis, while criteria expressed in terms of individual risk (e.g. probability of death per year for a specific person exposed to a risk) or societal risk (e.g. reference line in a FN diagram) can be applied for a system-based risk analysis. There are different methods of risk evaluation: it can be done by relative comparison, by a cost-effectiveness approach or by applying absolute risk criteria. However, in practice a combination of different approaches is often applied.

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Planning of safety measures: If the estimated risk is considered as not acceptable, additional safety measures have to be proposed. The effectiveness (and also cost-effectiveness) of the additional measures can be determined by using risk analysis to investigate the impact on the frequency or consequences of different scenarios. Planning of safety has to answer the question "Which measures are best suited to get a safe (and cost-efficient) system?

The simplified flowchart in Figure 2.4-1 illustrates the main steps of the risk assessment process. Risk assessment of road tunnels allows a structured, harmonised and transparent assessment of risks for a specific tunnel including the consideration of the relevant influencing factors and their interactions. Risk assessment models provide a much better understanding of riskrelated processes than merely experience based concepts may ever achieve. Moreover, they allow evaluation of the best additional safety measures in terms of risk mitigation and enable a comparison of different alternatives.

Fig. 2.4-1: Flowchart of the procedure for risk assessment

Hence, the risk assessment approach in the context of tunnel safety management can be an appropriate supplement to the implementation of the prescriptive requirements of standards and guidelines. In practice, there are different methods to approach different kinds of problems. It is recommended to select the best method available for a specific problem. Although risk models try to be as close to reality as possible and try to implement realistic base data, it is important to consider that the models can never predict real events and that there is a degree of uncertainty and fuzziness in the results. Considering this uncertainty, the results of quantitative risk analysis should be considered accurate only to an order of magnitude and should be supported by sensitivity studies or similar. Risk evaluation by relative comparison (e.g. of an existing state to a reference state of a tunnel) may improve the robustness of conclusions drawn but care should be taken in the definition of the reference tunnel. Basic principles and important components of risk analysis methodologies are presented in the : Technical Report 2008R02 "Risk analysis for road tunnels". This report also presents a survey of practical methods as well as a collection of case studies. The various approaches to risk evaluation are presented and discussed in a new report entitled: "Current practice for risk evaluation for road tunnels". This report also includes updates regarding risk analysis and is currently being finalised.

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2.5. Principles and tools for fire safety Among the possible risks to be considered in road tunnels, vehicle fires give rise to particular concern because they are not very rare events and their consequences may be far larger underground than in the open if no appropriate measures are taken. For this reason, several PIARC reports treat the is sue of fire safety in road tunnels. Part of the material included in these reports relates to specific tunnel features and is dealt with in the corresponding chapters of this manual, for instance:     

fire and smoke detection in Section 8.3, ventilation for smoke control in Section 8.5 fire-fighting equipment for the users and emergency services in Section 8.6 fixed fire fighting systems in Section 8.7 tunnel response to fire in Chapter 9.

However, before fire-safety measures can be defined, general principles, basic information on tunnel fires and study methods must be available. These are the issues dealt with in this section. On the basis of the general safety objectives for road tunnels stated in Section 2.1 above, more precise aims have been proposed for fire and smoke control:    

to save lives by making self evacuation by users possible, to make rescue and fire fighting operations possible, to avoid explosions, to limit damage to tunnel structure and equipment and to surrounding buildings.

These objectives are discussed in Section I "Objectives of fire and smoke control" of report 05.05.B , which includes a detailed discussion on tenability criteria under fire situations. Complementary guidance is included in Section 2 "Safety concepts for tunnel fires" of report 05.16.B. In order to help assess the risk and provide data to be used as a basis for design, information on the frequency of fires, design fires and design fire scenarios is given in Section II "Fire risk and design fires"of report 05.05B. Design fires for life safety considerations are normally specified as as either a constant or time-varying heat release rate, which is related to the assumed type vehicles on fire (e.g. one or more passenger cars or an HGV), and on the loads carried. Guidance on the selection of design fires is available from the PIARC report "Design Fire Characteristics for Road Tunnels". An understanding of how smoke behaves during a tunnel fire is essential for every aspect of tunnel design and operation. This understanding will influence the type and sizing of the ventilation system to be installed, its operation in an emergency and the response procedures that will be developed to allow operators and emergency services to safely manage the incident. Detailed discussion on the topic can be found in Section III "Smoke behaviour" of report 05.05.B and Section 1 "Basic principles ofsmoke and heat progress at the beginning of a fire" of report 05.16.B , which analyse in detail the influence of different parameters (traffic, fire size, ventilation conditions, tunnel geometry) in the development of an incident. To help scientists and designers, an exhaustive description of basic (full and small scale experimental results) and advanced (computer simulation) techniques available to approach fire safety studies is given in Section IV "Study methods" of report 05.05.B.

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2.6. Dangerous goods Dangerous goods are important for industrial production as well as everyday life, and they must be transported. However, it is acknowledged that these goods may cause considerable hazards if released in an accident, on open road sections as well as in tunnels. Accidents involving dangerous goods are rare, but may result in a large number of victims and severe material and environmental damage. Special measures are needed to ensure as safe a transportation as possible. For these reasons, the transport of dangerous goods is strictly regulated in most countries. Dangerous goods transport raises specific problems in tunnels because an accident may have even more serious consequences in the confined environment of a tunnel. The following questions must be addressed: 

 

Should dangerous goods movements be restricted in some tunnels, and what should be the basis for decisions on such restrictions? What type of regulation should be applied to restrict dangerous goods movements in tunnels? If dangerous goods are allowed, what risk reduction measures should be implemented, and what is their effectiveness?

From 1996 to 2001, the Organisation for Economic Co-operation and Development (OECD) and PIARC carried out an important joint research project to bring rational answers to the above questions: OECD. Transport of dangerous goods through road tunnels. Safety in Tunnels, Paris: OECD Publishing, 2001 ISBN 92-64-19651-X. The following paragraphs summarise the outputs of this project and the further developments.

2.6.1. Regulations regarding transport of dangerous goods through tunnels The first step of the joint OECD/PIARC research project was an international survey of regulations regarding the road transportation of dangerous goods in general and in tunnels. The survey showed that all investigated countries had consistent regulations for the transport of dangerous goods on roads in general, and that these regulations were standardised within large parts of the world. For instance, ADR (the European agreement concerning the international carriage of dangerous goods by road) is used in Europe and the Asian part of the Russian Federation. Most States in the USA and provinces in Canada follow codes in compliance with the UN Model Regulations. Australia and Japan had their own codes, but Australia has aligned with the UN system. In contrast, the survey highlighted a variety of regulations regarding the transport of dangerous goods through tunnels. Restrictions applied in tunnels showed considerable variations between countries and even between tunnels within the same country. The inconsistency of the tunnel regulations posed problems for the organisation of dangerous goods transport and led a number of vehicles carrying dangerous goods to infringe restrictions.. As part of their joint project, OECD and PIARC made a proposal for a harmonised system of regulation. This proposal was further developed by the United Nations Economic Commission for Europe (UN ECE), then implemented in Europe in the 2007 and further revisions of the ADR. The harmonisation is based on the assumption that in tunnels there are three major hazards which may cause numerous victims or serious damage to the tunnel structure, and that they can be ranked as follows in order of decreasing consequences and increasing effectiveness of mitigating measures: (a) explosions; (b) releases of toxic gas or volatile toxic liquid; (c) fires. Restriction of dangerous goods in a tunnel is made by assigning it to one of five categories which are labelled using capital letters from A to E. The principle of these categories is as follows:

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Category No restrictions for the transport of dangerous goods A Category Restriction for dangerous goods which may lead to a very large explosion B Category Restriction for dangerous goods which may lead to a very large explosion, a large C explosion or a large toxic release Category Restriction for dangerous goods which may lead to a very large explosion, a large D explosion, a large toxic release or a large fire Category Restriction for all dangerous goods (except five goods with very limited danger) E Table 2.6-1: List of the 5 ADR categories More information on this topic is available on the following websites:   

UN ADR 2009 documents website Australian ADG code website Canadian TDG regulations

2.6.2. Choice of the most suitable regulation for a tunnel Banning dangerous goods from a tunnel does not eliminate the risks, but modifies them and moves them to a different location, where the overall risk may actually be greater (diverting through a dense urban area for instance). For this reason, the joint OECD/PIARC research project recommended that decisions on authorisation/restriction of dangerous goods in a tunnel should be based on a comparison of various alternatives and should take into account the tunnel route as well as possible alternative routes. A rational decision process was proposed, with the structure shown in the figure below. The first steps would produce objective risk indicators, based on quantitative risk analysis (QRA). The last steps would take into account economic and other data, as well as the political preferences of the decision maker (risk aversion for instance). These later steps could be based on a decision support model(DSM).

Fig. 2.6-2: Rational decision process The OECD/PIARC project has developed a QRA model as well as a DSM. The QRA model is currently used in a number of countries. It is a system-based risk analysis model (see chapter 2.4 for definition) and produces indicators of the societal risk (F-N curves for the tunnel users and for the permanent neighbouring population), as well as the individual risk (for people permanently living in the neighbourhood of the tunnel) and damage to the tunnel and the environment. It is applicable both to routes including tunnels and to open-air routes, so that the risks on various alternative routes can be compared. The model is based on 13 accident scenarios representative of each of the five tunnel categories (although categories D and E cannot be distinguished because they lead to similar risks). This model can be bought from PIARC and is described in more detail in its website.


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Additional information as well as examples of application can be found in the following PIARC references: 



"Quantitative Risk Assessment Model For Dangerous Goods Transport Through Road Tunnels" in Routes/Roads 329 (2006) Section 4.6 "OECD/PIARC Dangerous goods QRA model" of report 2008R02 and Annex 3.7 "OECD/PIARC DG QRA model" of report 2008R02.

2.6.3. Risk reduction measures The joint OECD/PIARC research project also included an investigation of measures that could reduce the probability and/or consequences of an accident involving dangerous goods in a tunnel, where such goods are allowed. Firstly a state of the art was established, resulting in identification and description of all possible measures, most of which are described in part 2 of this manual (chapters 6-9). The second, more challenging step was an attempt at evaluating the cost-effectiveness of these measures with respect to dangerous goods hazards. Costs were not examined in detail as they will be specific to a particular tunnel project and can be studied for each individual project. The focus was put on the effectiveness of measures. Some of the possible risk reduction measures are directly taken into account in the QRA model developed under the project (see above). These were called "native" measures. The effectiveness of each of these measures, or each combination of measures, can be assessed by running the model with and without the measure(s) and comparing the results. A large number of tests were made and showed that no general conclusion could be drawn regarding the effectiveness of measures because the effectiveness very much depends on the specific case. Assessment of effectiveness should thus be made on a project basis. The effectiveness of the other, "non-native" measures was much more difficult to assess and methods were proposed to take a number of them into account. More information can be found in chapter VII of the OECD project report (Risk reduction measures).


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2.7. Safety procedures To ensure safety in road tunnels, the necessary structural, technical and organisational measures need to be put in place so that incidents can be prevented as far as possible and their impact can be kept to a minimum. The level of safety in tunnels is influenced to varying degrees by a variety of factors that can be collectively summarised in four main groups: Road Users, Infrastructure, Vehicles, and Operation. Most of the measures needed to ensure a safe tunnel are based on the above influencing factors and aim to prevent or mitigate the danger which arises from incorrect user behaviour, inadequate tunnel installations or operation, vehicle technical defects or other faults. See Chapter 1 "Why are tools for tunnel safety management needed?" of report 2009R08. All the above necessary safety measures have to be combined under effective tunnel safety management. To maximise the effectiveness of tunnel safety management, certain tools are needed to support strategy, to drive critical decisions and keep a constant and traceable focus on all safety issues, over a tunnel's lifetime. The three major "tools" for tunnel safety management are described below.

2.7.1. Road Tunnel Safety Documentation Safety documentation is a key aspect of safety management and should be compiled for each tunnel. The demands for this information are different depending on which stage the tunnel is at in its lifecycle: design, commissioning, or operation. At the design stage the safety documentation focuses on the description of tunnel infrastructure and traffic forecasts, whereas at the operation stage the operational aspects, such as emergency response plans and measures for transportation of dangerous goods, gain importance. The degree of detail in the information increases as the project develops. The safety documentation should comprise'living' documents which are continuously developed and updated; including detailing changes in tunnel infrastructure, traffic data, etc, as well as important findings from operational experience (i.e. analysis of significant incidents, safety exercises, etc.). More information is available on Chapter 2 "Road Tunnel Safety Documentation" of report 2009R08 .

2.7.2. Collection and Analysis of Data on Road Tunnel Incidents Collection and analysis of incident data, as detailed on Chapter 3 "Collection and Analysis of Data on Road Tunnel Incidents" of report 2009R08 are essential for the risk assessment of a tunnel and for the improvement of its safety measures. These comprise a two fold process, starting at the local tunnel level to cover specific needs, like input data for risk analysis, and extends to fulfil legal obligations such as reporting statistics at national/international level. The evaluation of specific events (accidents and incidents) may help to identify specific hazards in a tunnel as well as to optimise operational procedures and the reaction of safety systems. As well as analysis for real accidents, analysis of data from safety exercises can help to gain experience in the management of incidents under realistic circumstances.

2.7.3. Safety Inspections of Road Tunnels Safety inspections, as explained in Chapter 4 of the technical Report 2009R08 (Safety Inspections of Road Tunnels) are a tool to assess the current tunnel safety level either within a legal framework (European Directive for instance) or against an accepted level of risk. PIARC has developed an organisational scheme based on the EU Directive 2004/54/EC to describe the chain of safety responsibility concerning safety inspections and clarify the responsibilities of the involved parties. It also proposes the contents of a safety inspection (infrastructure and systems, safety documentation and existing procedures, tunnel management organisation, training and quality assurance) along with a comprehensive roadmap with all the necessary steps and preparation needed to carry out a safety inspection.

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2.8. Assessing and improving safety in existing tunnels 2.8.1. Why upgrading existing tunnels As a consequence of the major disasters in road tunnels (Mont Blanc tunnel fire in 1999, Tauern tunnel fire in 1999 or Gotthard tunnel fire in 2001), specific attention was turned to the safety standards of existing tunnels. Existing tunnels require specific approaches and tools to identify and evaluate the need for safety upgrade programmes. Substantial research and studies followed these major tunnel fire incidents, demonstrating that many existing road tunnels require additional and specific means to ensure a safe environment for users. Even where previous improvement programmes have been carried out, existing tunnels may not be in line with the current safety standards because of upgrading of regulations in the meantime. These incidents and subsequent studies have raised awareness of tunnel risk amongst individuals involved in road tunnels from designers and operators to authorities' representatives. It has become clear that safety upgrade is not only a matter of improving the structure and/or equipment, but that there is also, and sometimes mainly, a strong need to clarify safety management organisation and to adapt procedures. In the assessment of safety in existing tunnels, special attention should be paid to changes in the tunnel environment (traffic volume and composition, dangerous goods transport, construction works in the surrounding area, etc) which may also induce the requirement for upgrading measures.

2.8.2. Proposed methodology to assess and improve existing tunnels A structured approach for assessing and preparing refurbishment programmes is proposed with two main tasks: 



The first task aims to assess the current situation of the tunnel, like an instantaneous picture of the tunnel, in order to identify the current safety level. First of all a reference safety level must be defined, which is generally provided by regulatory frameworks. Then the current tunnel functionalities and the state of the facilities which perform them have to be analysed. On this basis it must be assessed whether the existing tunnel is currently in line with safety-relevant design criteria. Furthermore, specific risks should be assessed by risk analysis which is an appropriate tool to evaluate the current safety level of a tunnel in operation. From these initial analyses, actions can be defined and priorities can be set The second task aims to define the future tunnel situation after renovation works which can be acceptable in relation to the defined safety level goal. This can be done by developing renovation programmes and assessing again the safety level of the renovated tunnel including all upgrading measures. Once again risk analysis can be applied to demonstrate an adequate safety level or to evaluate various alternatives of upgrading measures, including cost-effectiveness criteria. Renovation programmes depend on the specific context of each tunnel, its constraints and its environment. An iterative process of risk analysis may be followed where agreement is reached on a projected safety level that is acceptable to all stakeholders in the project.

The multistage process for the preparation of a tailor-made renovation programme for a tunnel in operation can be summarised in the flowchart below. It describes the functional links between the various steps and their respective outputs. In detail, the content of each step is to be adapted to the specific conditions of the individual tunnel, its environment, and of course specific local practice. Depending on the tunnel situation, the process can be stopped after step 3 with a simple comparison to the reference state if the analysis is demonstrating that the required safety level is already achieved. Indeed, for tunnels already renovated, step 3 can be the end of the process.

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Fig. 2.8-1 : Flowchart of the multistage process If not, step 3 may highlight urgent mitigation measures which canbe implemented immediately to improve the tunnel safety level with non-substantial actions such as closure barriers, signalling or traffic control measures. In some cases, such measures may be sufficient to obtain the required safety level. If more substantial works are required, temporary modifications of the operating conditions may be a useful tool for a temporary increase in the tunnel safety level, if necessary. The preparation of renovation works for a tunnel in operation is an iterative process as it is a combination of technical issues, safety measures, costs implication and works phasing constraints. This is why step 4 and 5 can be refined several times to obtain an adapted refurbishment programme taking into account all relevant parameters which may influence the decision. Design activities can start after step 5. The new report "Assessing and improving Safety in Existing Road Tunnels" provides guidelines for each step within this process, up to the definition of an improvement programme. Typical weak points (safety deficiencies) in existing tunnels are presented. Additionally, case studies of existing tunnels in Europe demonstrate the strategy adopted for renovation works and upgrading measures implemented.

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3. HUMAN FACTORS REGARDING TUNNEL SAFETY



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3. Human factors regarding tunnel safety The PIARC Technical Committee on Road Tunnel 0peration has felt the need to provide a better understanding of human behaviour in tunnels in both normal and critical situations and to provide recommendations for tunnel design and operation based on this understanding. This knowledge of human behavior is decisive to act accordingly towards: 



the user himself and the infrastructure (in particular so as to optimize the communication devices and design of safety facilities including those dedicated to self evacuation), the tunnel operating body and emergency services who must be able at all times to coordinate to ensure optimal management of the event.

An adequate knowledge of human factors in the context of road tunnels optimises safety by acting in the direction of the user, the tunnel design and more generally, the organisation (tunnel operating body and emergency services). The whole tunnel system, including the organisation of tunnel management, plays an important role in tunnel safety as it determines what the tunnel users see or have to respond to, in both normal and critical situations. The nature of the traffic regulations, motorists' compliance with them and the degree to which they are enforced contribute significantly to the level of tunnel safety. The properties of the vehicles using the tunnel and the loads they carry also play an important role. Additional measures (with respect to the minimum requirements set by the EU-Directive) could be considered when focussing on human factors and human behaviour in terms of tunnel safety. At this stage, the focus of this chapter is on the interaction between the tunnel system and tunnel users; additional information is provided regarding the interaction with tunnel staff and emergency teams. The main conclusions regarding tunnel users are that (see details in Section 3.1.):   

 

the design of tunnels and their operation should take account of human factors; drivers need to be more aware of how they should behave in tunnels; a fairly long stretch of road (if possible 150 - 200 m) before the tunnel portal should not contain too many signs and signals; the necessary signs and signals at the point of entry into the tunnel should be strictly limited in number; the tunnel safety facilities should be easily recognisable even in normal traffic; alarm signals should be provided by multiple-redundant sources.

Regarding tunnel operators and emergency teams it can also be concluded that it is of utmost importance for operator's staff (see details in Section 3.2.) and emergency services (see details in Section 3.3.):  

 



to organize consultation and cooperation during the tunnel design process, to construct contingency plans in order to prepare for tunnel user protection and fire fighting operations, and to keep these plans up-to-date, to organize familiarisation visits to tunnels and arrange exercises to test operational training, to define the measures necessary to minimise the time required to mobilise the emergency services, to organize post accident analysis, including events of limited importance.

Designing for optimal human use should include assessment of human abilities and limitations and ensuring that the resulting systems and processes that involve human interaction are designed to be consistent with the human abilities and limitations that have been identified. Human abilities and limitations refer to those physical, cognitive and psychological processes that deal with perception, information processing, motivation, decision-making and taking action. General recommendations are presented in Section 3.4.

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Contributors

This chapter of the manual was written by Marc Tesson, associate member of C4 committee and leader of working group n° 3 "Influence users' behaviour". The previous leader of this working group, Evert Worm, contributed to the production of the English version. Didier Lacroix, the former Committee Chairman, re-read the French version.

Fig. 3.0-1: Emergency exit

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3.1. Users The following aspects are emphasized in Technical Report 2008R17 "Human factors and road tunnel safety regarding users". 

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models that describe the human decision-making process: these are intended to give tunnel professionals a brief theoretical background giving insight into human behaviour: Chapter 1 "General aspects of human factors" of report 2008R17 observations of the behaviour of tunnel users in both normal and critical situations and Fig. 3.1-1: User approaching a tunnel discussion, in general terms, of the main human factors that influence this behaviour: Chapter 2 "Human behaviour in road tunnels in normal situations" of report 2008R17 and Chapter 3 "Human behaviour in road tunnels in critical situations" of report 2008R17 general aims of safety features, followed by a description of the minimum measures required by the EU directive: these measures are examined in the light of results of psychological research and recommendations from other sources to finally formulate recommended additional measures: Chapter 4 "Recommended additional measures to improve road tunnel safety in normal traffic conditions" of report 2008R17 and Chapter 5 "Recommended additional measures to prevent escalation of critical traffic conditions in road tunnels" of report 2008R17 models that describe the human decision-making process: this is of interest for the interface between tunnels and tunnel users: Chapter 6 "Future development of ITS and tunnel safety" of report 2008R17.

When carrying out these investigations the Working Group members involved in these studies often had to answer the following question: "should we adapt the tunnel to the user or the user to the tunnel?" Obviously both strategies should be made use of, and in order to put the existing recommendations into perspective the Working Group decided to investigate the subject of driver education and information for drivers. The following aspects will be emphasized in the planned report "Recommendations regarding road tunnel drivers' education and information". The goal of this report will be to provide recommendations to all those in charge of education and information actions: national organisations and agencies, owners, operators, and consultants in the field of communication. In the first chapter this report will provide general information for the target readers who it is assumed have little if any knowledge of the details of the tunnel context. The second will deal with general recommendations valid for all target readers and/or institutions. Chapters 3 and 4 will propose recommendations for the attention of organisations and agencies, and specific owners.

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3.2. Operators The term "operator" describes the body representing the owner on site and responsible for operating the tunnel. This key player for tunnel safety works in close relation with the other players concerned (owner, public authorities, emergency services, sub contractors, other operators, users, etc). Its main task is to manage traffic, civil engineering aspects and tunnel equipment, together with crisis and administrative management related with its missions. It plays a crucial role for optimum implementation of the tunnel safety managament system: this is demonstrated by its Fig. 3.2-1: Road tunnel command post involvement in design studies (including risk analyses) and definition of operating principles, not forgetting the day-to-day monitoring of tunnel operation (event management, carrying out safety exercises, implementing experience feedback, regular updating of operating documents, staff training, coordination with other bodies involved, etc). With respect to this player, the following aspects are highlighted in the existing Technical Report 2008R03 "Management of the operator-emergency teams interface in road tunnels" : 

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most relevant lessons learnt from the most serious tunnel fires of the last decades: Chapter 1 "Lessons learnt" of report 2008R03 information and recommendations for best practice. These are based on experience and lessons learnt: Chapter 2 "Detailed recommendations" of report 2008R03.

More generally the lessons learnt from exercises and real events have shown that the behaviour of all those in charge of operating the tunnel is a decisive factor in ensuring the safety of people during an incident. One of the key issues regarding this topic is appropriate reaction of the operating staff responsible for monitoring and controlling tunnels. They are the very first to be involved in road tunnel crisis management and as such carry very considerable responsibilities on behalf of the operator in terms of daily tunnel management. Their task is all the more difficult in that they may at any time be required to manage potentially serious events for which the probability they will happen is extremely low. To react in the appropriate manner, tunnel operators must be able to understand and control sometimes complex situations, meaning they must be very good at stress management. Specific and appropriate training is thus essential. European regulations require the personnel involved in operating tunnels to receive "appropriate initial and continuing training" (European Directive 2004/54/CE - Annex 1 § 3.1 "Operating means").

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3.3. Emergency teams Rescue teams liable to be called on to intervene in road tunnels obviously need to have the general training required to help people and combat fires in any type of infrastructure. Tunnels are confined spaces in which a crisis or fire can very quickly render rescue operation conditions more complicated. Over and above their technical skills, firemen therefore need to be trained specifically for this type of intervention. This training must develop their behavioural knowhow and enable them to deal appropriately with the complex situations they may be confronted with in a tunnel. This knowhow is particularly Fig. 3.3-1: Tunnel safety exercise with fire brigade crucial for the supervisory staff who must be capable under all circumstances of adapting the operational methods initially envisaged, if needed. In order to fulfill this mission, good coordination with the tunnel staff is decisive, requiring meticulous preparation, followup and implementation of intervention plans, safety exercises, and training based on feedback of experience. In the case of cross-border tunnels, attention needs to be drawn to the collaboration required between the countries concerned in order to ensure perfect coordination between the rescue teams in crisis situations. With respect to the rescue teams, the following aspects are emphasized in Technical Report 2008R03 "Management of the operatoremergency teams interface in road tunnels" : 

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the most relevant lessons learnt from the most serious tunnel fires of the last decades : Chapter 1 "Lessons learnt" of report 2008R03 information and recommendations for best practice. These are based on experience and lessons learnt: Chapter 2 "Detailed recommendations" of report 2008R03.

Fig. 3.3-2: Helping users in a shelter

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3.4. General recommendations This paragraph provides general recommendations to those who intend to pay particular attention to human factors when designing a new tunnel or refurbishing an existing one. Its objective is not to sum up the fundamental technical recommendations developed in the PIARC reports regarding inclusion of the human factors when considering safety. It aims above all at summing up the main methodological recommendations to be implemented when it is desired to pay particular attention to these aspects. Three main points deserve to be underlined from this viewpoint: 1. the need to intervene as far upstream as possible in the framework of studies, 2. the crucial importance of taking account of the work carried out in the field of integration of human and organisational factors in safety, 3. the advantages of tests to validate innovative solutions liable to be implemented. The first point particularly concerns the design of new tunnels for which it is fundamental to intervene as far upstream as possible during the studies. This should allow better account to be taken of the main factors which govern the behaviour of users in road tunnels. Among these main factors, the following can be notably mentioned: 

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data related to the local context, for example, the type of traffic and thus the users concerned (locals, professionals, subscribers, etc.), contextual items related to the existing infrastructures upstream and downstream from the planned tunnel (route continuity logic), other tunnels on the route or in the neighbourhood of the tunnel, cross-border tunnels for which particular attention must be given to the strategies and means implemented to communicate with the users.

The second point concerns consideration of the work carried out in the field of integration of human and organisational factors with respect to safety, notably aiming to make best use of knowledge accumulated to date in the field of general road safety, and evacuation in crisis situations in particular. This can take shape in two ways: either by referring to general lessons learnt from work carried out in this field (PIARC recommendations for example), or by involving human science specialists (psychologists, experts) in the project. The advisability of involving human science specialists deserves to be considered both for the design of new tunnels and for the refurbishing of existing ones. Obviously it applies only for the most important projects with particular issues (cross-border and/or particularly long tunnels, tunnels of limited dimensions, etc.) In this field and as is already the case for open-air infrastructures, it is necessary to remain very prudent before implementing a technical solution which appears at first sight to be satisfactory. The lessons learnt from real events or from the numerous exercises held in tunnels do indeed show that the technical choices made by engineers specialised in the fields of equipment and safety in tunnels are not always the most appropriate from the viewpoint of user behaviour. Independently of the possible implication of human science specialists, it is obviously necessary to take care to ensure a wide consultation of all the actors concerned at all times. In particular, the intervention services must be closely associated with the design of the safety equipment (particular attention must be given to features provided for self-help for evacuation of users). The third recommendation concerns the tests and trials necessary to validate innovative choices when the latter prove to be desirable. Much has already been learnt in terms of taking human behaviour in tunnels into account. Designers are invited to pay attention to these factors when finalising all the safety measures in tunnels. When it proves to be necessary to develop innovative means, the preliminary test phases must not be neglected (indoor testing for example), nor trials on site. These trials could be usefully performed with support from experts in the field of human sciences. Their objective will be to validate the innovative measures proposed before deployment in tunnels. As a conclusion and in general, we cannot but recall the need to show much pragmatism and humility in this field. A basic principle consists in preferring simple and intuitive solutions whenever possible,

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in line with what is currently in practice in non-confined conditions. These types of approach guarantee that the measures implemented are liable to be well understood and adopted by the users.

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4. OPERATION AND MAINTENANCE



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4. Operation and maintenance Operation and maintenance are clearly an important issue for a PIARC Committee that a few years ago changed its name to the Committee for "Road Tunnel Operations". Operation and maintenance activities can be considered as divided into three main streams of activity: 1. Daily management: this stream includes all activities to monitor the traffic and to cater for an efficient functioning of all equipment during normal operations and in the case of an emergency, to ensure the proper functioning of all structural and electro-mechanical installations. 2. Training of the staff: this is normally a multi-organisation task, considering that normally not only the operator, but also traffic police, fire brigade and other emergency services who cooperate to deliver an acceptable level of safety in road tunnels. It includes: the basic training of the staff, exercises, etc. 3. Continuous improvement of safety: this includes all actions of study and planning aiming at a continuous improvement of safety (emergency planning, feedback of experience from accidents, replacement of tunnel equipment, etc.). Efficient operations and a cooperative environment among different stakeholders in charge of tunnel and emergency management clearly underpin the safety and comfort of users and operators both in normal operations and in the event of an accident Considering the European context, the Directive 2004/54/CE on "Minimum safety requirements for tunnels in the trans-European road network" clearly states that safety is not only related to structures and equipment. In fact the directive identifies a special role for activities related to Operation and Maintenance. In order to successfully and efficiently operate and manage a road tunnel, operational tasks and the responsible body for carrying them out, need to be established in order to ensure that all actions required are handled in a consistent and safe way ( Section 4.1). The level of safety provided for tunnel users is highly dependent upon the specific characteristics of the tunnel, but it also depends strongly on operational procedures and the people who are in charge of the tunnel. The people in charge do not necessarily need to belong to the same organisation: players and roles can be quite different. For example, the traffic police are normally in charge of traffic, but the task is sometimes carried out by a road administration, and in some cases several tasks are entrusted to a private company/operator. Moreover, the same task (for example: traffic management) can be performed by many different bodies (operating staff, police, subcontractor), so the relative roles and responsibilities have to be specified as well as recommendations to improve the behaviour of people involved in tunnel operation and their level of cooperation ( Section 4.2). In each case the organisation of the operation and coordination with all the different bodies must be defined, by written procedures and protocols that are simple and straightforward, so that they are clearly understood by all parties and are robust under pressure in emergency situations. The organisation of the operation can be quite different from one tunnel to another; consequently it is difficult to define an overall common framework. However, it is convenient to assess for each tunnel or group of tunnels the best-fit organisation to be adopted both during the standard operation and in the event of an emergency situation ( Section 4.3).

Moreover it is essential to establish standard operating procedures as well as minimum operating conditions and emergency plans. This is in fact a key step in planning the operational response to possible tunnel emergencies for which there need to be appropriate specific responses to various types of incidents (Section 4.4).

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The management and day to day operation, as well as the maintenance of a tunnel, involve high operational costs and funding requirements. In fact tunnels are among the most costly parts of a road network to be operated (in terms of energy requirements, staffing and monitoring). The definition and optimisation of the different cost elements in a tunnel and appropriate recommendations to reduce them have been analysed by the PIARC tunnel committee. The efficient use of energy and the progressive reduction of energy consumption should be considered, with a view to delivering a sustainable operation of the road network (Section 4.5). The final objective is clearly to guarantee an appropriate level of service and quality to the users. The achievement of the objective obviously depends on the nature and overall performance of the facilities and equipment. The performance of the equipment often depends on how this equipment is operated by the tunnel staff in terms of timeliness and appropriateness. Therefore the staff called to perform operational tasks must be well selected when recruited, well trained before starting their tasks and continually throughout their careers (Section 4.6). The safety level or the traffic capacity in a tunnel are influenced by changes characterising the road network and the evolution of the traffic itself. The tunnel operator may occasionally need to make minor or major changes to the system or to the management criteria to cope with these changes. It is therefore necessary to monitor changes and accidents using information and feedback, to continuously and systematically improve tunnel operations. The operator needs to receive feedback from the experience of operation to be used to make choices for the improvements (Section 4.7). Structural elements and the technical equipment need regular maintenance whose goal is to ensure safe driving conditions for the public by keeping the tunnel at its designed safety standard ( Section 4.8). General recommendations for maintenance in tunnels are defined as well as the speci fic features and their facilities. When the tunnel equipment no longer satisfies the needs of the operator, the requirements of legislation or when the nature or the level of traffic changes, it may be necessary to upgrade or refurbish the tunnel. For the refurbishment of an existing tunnel , recommendations mainly concerning measures to facilitate the management of traf fic network, equipment reliability and durability and whole life costing are defined ( Section 4.9). The present chapter 4 essentially concerns tunnels of medium to long lengths, with medium or heavy traffic volume, located in places where prompt external emergency interventions are possible.These tunnels are operated with a specific organisation, dedicated to one tunnel or a group of tunnels, which are part of the same road network. Section 4.10 presents the specific conditions concerning short tunnels, or very low trafficked tunnels, or scattered tunnels situated in areas with low population densities.

Contributors

This Chapter was written by Working Group 1 of the C4 committee (2008-2011) in which:   

Roberto ARDITI (Italy) authored section 4.0 and coordinated the work; Jean-Claude MARTIN (France) authored sections 4.1 to 4.10; Fathi TARADA (UK) reviewed the full chapter.

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4.1. Operational tasks Generally speaking tunnels are considered as parts of the road network able to ensure a suitable or even higher level of safety, nevertheless the potential consequences of specific incidents (breakdown, accident or fire) may be far more serious in tunnels than in the open air. Moreover, the tunnels being very often obligatory crossing points and maybe bottlenecks of the network, each total or partial closure can lead to major disturbances of traffic or can oblige users to travel long distances on alternative routes. Because of these reasons, operators and road authorities have to ensure the operational continuity and safety of road tunnels. Therefore, they must guarantee to the users crossing the tunnel a level of service quality and safety complying strictly with regulatory requirements in force. According to national regulations, tunnel operators and traffic police have to manage the traffic in the tunnels (and in the route where the tunnel is located). Specifically, they need to cater for the safety inside the tunnel for users and for people working inside the tunnel (operating staff, sub-contractors, etc.). In several countries, the traffic police are in overall charge of traffic management and traffic patrolling, while the operator is in charge of operational tasks such as maintenance, operation of tunnel equipment, traffic surveillance and traffic assistance. Generally speaking, typical tasks for the operators are: 

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Traffic surveillance and operation of tunnel equipment Major tunnels (in terms of length, traffic density and complexity of the tunnel) are usually managed from a Traffic Control Centre. Very often, the Control Centre is equipped with remote surveillance systems (e.g. television closed circuits, automatic incident detection) and can remote control certain equipment (ventilation, signalling, closing the tunnel, etc.). Technical Patrolling In certain cases, the operator can also deploy patrols that can provide a direct surveillance of the users by patrolling in the tunnels. These patrols can intervene very rapidly in case of need. Management of civil engineering works This means a permanent surveillance of the civil engineering works of the tunnel by conducting regular surveying and inspections. It also means carrying out regular maintenance of facilities such as drainage systems, gutters and all secondary structures (premises inside the tunnel, technical rooms, etc.), Management of equipment In major tunnels, the operator deploys several types of equipment that in the operation phase are under his own control. To this purpose tunnels are also equipped with systemsthat allow the operator to monitor the status of equipment. The operator must also cater for the maintenance of equipment fitted in the tunnel. Here again, it is possible to have access to computerised tools for assisting him in performing this task. Management of emergency situations Whatever the nature of the accident, whether it is a problem related to traffic (accident, interlinked accidents, fire, etc.) or to equipment (loss of power supply, malfunctioning of data transmission network, etc.), to intervene or to inform/activate the pertinent service/authority is the standard duty of the operator in charge of the surveillance. Technical and Administrative management In addition to tasks directly related to the tunnel operation, the operator provides the technical and administrative services supporting the management of the infrastructure and, of course, the personnel. The operator caters for the design of any equipment upgrading, the direction of the works, the investment and operational budgets for the proper functioning of the tunnel. Lastly, the operator also develops statistics and monitors the achievement of its own objectives by preparing periodical reports on the operation of the tunnel/route (financial indicators, traffic indicators, etc.).

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The Technical report 05.13.B "Good Practice for the Operation and Maintenance of Road Tunnels" deals with this subject in parts 2 and 4.

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4.2. Players in tunnel operation and their co-operation The management of the road transport process is a very complex task. It is even more complex if we consider the road transport into a tunnel environment. Part of the complexity is also related to the fact that skills and competencies required for the management of tunnels are scattered among different services. To this purpose, the cooperation of different stakeholders is clearly a vital pre-requisite for a fair and effective cooperation, in order to deliver good traffic and incident management. The coordination is normally performed under the umbrella of local or central authorities that coordinate the process and finally record the result of programmes as approved by inter-organizational committees. The main stakeholders that need to cooperate in this frame are: 

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The tunnel operator; The operators of different parts of road network who have to be notified in case of tunnel closure or traffic restrictions, as part of a common traffic management on the route/network; National and local administrative authorities to whom reports have to be submitted as required under the regulations; The owner of the tunnel (if it is not the same as the operator of the tunnel), who also has to be kept informed; The public services (fire and rescue services, traffic police, medical services...) with whom coordinated intervention plans have to be prepared so that they can intervene in a coordinated and efficient manner in response to any types of incidents; Other sub-contractors (cleaning, maintenance, breakdown services for users, etc.)

The Technical Report 2007R04 "Guide for organizing, recruiting and training road tunnel operating staff" defines the organisational tasks in a more precise manner.

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4.3. Organisation of operations The operational tasks (operation, maintenance, etc.) can be considered as similar for a wide range of tunnels, even of the internal organisation of entities responsible may be very different depending on the country, and where different tasks can be either be performed by the operator or delivered by other bodies. In some cases, a single organisation can cater for all the personnel required. In other cases, t he operational tasks may be shared by several public and private organisations. The tunnel owner or the road administration may for example entrust different public or private organizations to take charge of the tunnel construction and operation as a whole and/or specific operational tasks(e.g. the maintenance tasks can be handed out to contractors). The measures planned for managing incidents may be different, depending on national regulations and also according to local requirements specific to each tunnel. The organization of the operator and the traffic police can consequently be different, depending on the local context. Even though the context varies greatly from one country to another, very generally, the structure of the operation is organised into three principal groups:  

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The operating staff, in charge of operation management and traffic assistance; The technical staff in charge of the construction and management of the tunnel (civil engineering and equipment); Administrative personnel; Emergency rescue services (in a few cases, are also part of the operating staff).

The Technical Report 2007R04 defines in its chapter 4 "Operating staff: tasks and facilities" the organisation of operation in greater detail.

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4.4. Operating instructions, minimum operating conditions, emergency plans Every tunnel operator produces and updates written procedures (sometimes called "operating instructions") which define the objectives and criteria of possible actions by different internal service providers, which can affect the tunnel or road. All types of operational events need be taken into consideration for the procedures, including routine incidents, serious accidents and emergencies. The'operating instructions' contains the basic actions to be carried out with associated procedures and existing constraints. The operator's staff also need an emergency plan for both intervention after a road accident and technical failure of equipment in the tunnel. This plan usually meets regulatory requirements and includes operational procedures and instructions involving, at minimum, the tunnel operators and the intervention personnel in case of incident or technical failure. The emergency intervention procedures should be coordinated with those applied by emergency and rescue services. The detailed content of this plan could be defined by national instructions or directives specific to each country and needs to be tailored to the technical and organizational framework of the tunnel. The Technical Report 2007R04 defines in its chapter 4 "Operating staff: tasks and facilities" the organisation of operation in greater detail.

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4.5. Operational costs Experience shows that a kilometre in tunnel is always more costly than a kilometre of the same road outside. In the case of an underground structure, we can find several systems and equipment that are deployed either for ensuring a safe operation under standard operating conditions or for allowing the protection and the evacuation of users and the intervention of rescue services in case of incident, accident or fire. These measures not only represent considerable investment costs but also result in particularly high costs for operation and maintenance. Thereby the role of the operator is to ensure the continuity and the safety of the operation in a context of controlled costs. In all cases, even a high standard of tunnel operation may not allow an optimisation of operational costs, if the design and the construction of the tunnel have undertaken to a low quality level. The operational costs therefore need to be a major concern during the different phases of the project and the work execution, considering that the solution need to be found well before becoming an issue during the operational phase. The operation activity has to be designed at an adequate level in order to ensure that the expected lifecycle of the equipment does not decrease. The lifecycle of equipment in tunnels is normally shorter than in other environments, since the atmosphere in tunnels particularly corrosive. The Technical Report 05.06.B "Road Tunnels: reduction of Operating Costs" is entirely devoted to operating costs and in particular, to reducing them.

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4.6. Staff recruiting, training and exercise Tasks entrusted to the operating staff are very important in the light of safety and efficiency of the operation. Moreover, the context is evolving, because on the one hand, the operational problems assume greater importance compared to purely technical problems and on the other hand, the operating systems are more and becoming complex. The staff in charge of the operation need therefore to satisfy the following requirements:    

They should be well selected through a recruitment process They should be well trained before taking up their functions They need refresher courses throughout their career They should participate in exercises, possibly organised in cooperation with external services.

During recruitment phases, the qualifications required for the future operators must be defined according to the nature of operational tasks. It may be remembered that even if the tasks are similar in all countries, the people responsible for executing them do not necessarily belong to the same kind of organisation in each country. Nevertheless, the skills and aptitudes required should be similar. While designing the staff training (initial or permanent), the following two issues need to be addressed: 

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What kind of training need to be provided to the operating staff (or, what should be the obligatory training)? What criteria are to be applied by the operation manager for validating the quality of the training and the results obtained?

If there are no national rules on the content of training, the operator has to adapt his training programme to the specific characteristics and requirements of his tunnels. The Technical Report 2007R04 "Guide for organizing, recruiting and training road tunnel operating staff" specifies the recruitment and training of personnel in greater detail, chapters 7 " Recruitment of operation staff" and 8 "Training operating staff" . The operator needs to test regularly the efficiency of his personnel and the procedures he has set up. Thereby the operator needs to make sure that his staff are familiar with the different equipment installed in the tunnel and he can thus detect any possible deficiencies in the execution of specific tasks. In addition to internal exercises, the operator and emergency services need to organise jointrescue exercises with the participation of the traffic police, the operator, medical services and the fire and rescue services. The results of each exercise should be analysed. If lessons drawn from an exercise reveal lacunae, the intervention strategies should be reviewed. A new Technical Report on "Good practice for road tunnel Emergency exercises" will be available soon in the PIARC Virtual Library.

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4.7. Feedback from operation and incidents The collection of data regarding incidents and accidents and their analysis is essential both for the evaluation of the operation criteria and for the asses sment of risks in the tunnel. All of this is important with a view to a continuous improvement in tunnel safety. The collected data allow, in particular, the evaluating of the frequency of triggering events. Data also provide a feedback regarding the consequences of events and also the effective role and the effectiveness of safety measures and equipment. They also provide additional information on the real behaviour of tunnel users. The collection and analysis of data regarding incidents and accidents should allow the following two objectives to be achieved: 

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At a local level (i.e. at the level of each single tunnel): they form an important base for the definition and evaluation of improvement to be decided by the owner of the tunnel. They are also a decision-making aid for the general improvement of safety in a given road network; At a national and international level: they form a key basis for the reference framework allowing authorities to formulate and adapt the general policies related to tunnel safety. In particular, they allow quantifying the magnitude (in terms of frequency and severity) of critical events that can cause a danger to the life of users. They also allow measuring the efficacy of safety installations and in certain cases, comparing the level of safety in a given tunnel with national or international safety data.

Lastly, they provide information (national statistics according to the type of tunnel) useful for the analysis of risks relating tunnels in project stage or tunnels under operation that do not yet have an adequate database. The lessons drawn from the operation, particularly during incidents and accidents, should be analysed. In fact if the results of these analyses reveal deficiencies, there is an opportunity to intervene by improving strategies and/or operating instructions. The Technical Report 2009R08 "Tools for road tunnel safety management" defines in detail the conditions for analysing data from incidents and/or accidents in its chapter 3 "Collection and analysis of data on road tunnel incidents" .

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4.8. Maintenance of equipment Throughout the life of the tunnel, the operator should carry out both the maintenance of civil engineering works and the tunnel equipment. The maintenance of civil engineering structures is not described in this paragraph. The maintenance operations on equipment can be classified into two groups: 

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The preventive measures that are carried out at fixed intervals with the objective of preserving the equipment in a good operating condition. Preventive maintenance offers the advantage of preventing, as far as possible, unforeseeable failures and, by the way, it is easy to plan in advance. It can however lead to high costs if the interventions are too frequent: therefore, they need to be optimised suitably. The corrective actions that are carried out when a system or a part of a system has failed or been damaged. Corrective maintenance offers the advantage of using a system to the maximum extent of its service life. Its disadvantage however is that it cannot be planned and therefore emergency repairs are normally carried out with a significant surplus cost.

It is recommended to use preventive maintenance where possible and for those systems that are not redundant and are related with safety. Preventive maintenance allows the joint planning of different maintenance tasks in the event of every closure of the tunnel to the traffic. Moreover it helps keep the equipment in a good operating condition. It may be noted however that even when preventive maintenance is carried out very well, the operator cannot avoid corrective interventions. Usually the operator's staff do not carry out all maintenance tasks; the operator normally entrusts contractors and several options are consequently available: 

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It is possible to contract only those maintenance tasks related to a specific technical level. The operator can thus contract tasks that present no technical complexity (cleaning, washing, ...) or it can contract only very complex tasks (supervision system, radio retransmission equipment, ...) It is possible to contract all tasks of one or more equipment groups (all ventilation systems, all remote surveillance installations, etc.).

The Technical Report 05.06.B in its chapter 7 "Cost of maintenance ", the Technical report 05.13.B in its chapter 4 "Maintenance and operation" and the Technical Report 2007R04 in its chapter 6 "Organising operating staff", give more complete information on the subject of maintenance.

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4.9. Operation during maintenance and refurbishment works Maintenance tasks are not very different from one tunnel to another for similar equipment. However, some tunnels have specific features (dense and non-stop traffic, very long diversion route, etc.) that make total or even partial closures of the tunnel very difficult. In this case, the operator may have to maintain a certain operational level, while maintenance interventions are being carried out. This is possible only by deploying special measures that should take into account not only the safety offered to the user but also the safety of the maintenance staff. The Technical report 2008R15 in its chapter 2 "Operation of existing urban road tunnels" defines the conditions for carrying out maintenance when the tunnel is in operation. The same difficulties as those mentioned above are likely to be encountered during a refurbishment of equipment in a tunnel that cannot be closed down easily. With regard to maintenance interventions, this type of works may require several weeks, or even several months to be completed. Consequently, more elaborate (and often costlier) measures have to be planned. The Technical report 05.13.B discusses aspects relating to refurbishment in its chapter 6 "Renovation of tunnels" .

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4.10. Short tunnels and/or very low trafficked tunnels The recommendations presented in sections 4.1 to 4.9 above are not always relevant (or even difficult to implement) for short tunnels, or very low trafficked tunnels, or scattered tunnels situated in areas with low population densities. For these particular tunnels, it is recommended to carry out for each tunnel (or group of tunnels located on the same road network) a detailed specific analysis taking into account:  

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geographical and climatic conditions, local or regional resources available in the neighbourhood: authorities, operator, emergency services, etc., economic context, exposure to risk and level of risk.

This analysis will then make it possible to organise and to implement the most suitable operating system, according to the specific conditions of these tunnels.

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5. ENVIRONMENTAL ISSUES LINKED WITH OPERATION



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5. Environmental issues linked with operation Increasingly, road designers select tunnels as a good alternative, considering the ability of road tunnels to reduce some components of the environmental impact such as visual intrusion of infrastructures and noise pollution. Nevertheless some impacts remain or are even increased by such a choice. Despite all policy efforts to try to control and even reduce traffic, it is expected that traffic will increase during the next decades; so environmental issues linked to road traffic need to be considered. The PIARC tunnel committee deeply and specifically investigated air pollution phenomena considering: 1. Pollution inside tunnels as the technical basis for the dimensioning of road tunnel ventilation systems; 2. Pollution outside of the tunnel as direct evolution of know-how within the committee. In fact, when considering air pollution, choices concerning the type of ventilation system determine the basis for designing the locations and flowrates of exhaust air; the operation regime and air quality set points for the ventilation control can often be more effective in delivering the required targets for local pollutant concentration than the selection of more complex ventilation systems. Road traffic and (consequently) vehicle emissions constitute a serious environmental concern particularly in confined spaces as tunnels. These emissions are characterized by the presence of various pollutants, which, at high concentrations, can cause adverse effects and consequences. The PIARC tunnel committee traditionally assesses vehicle-induced emissions and air quality inside tunnels. To this purpose, common modelling theories are reviewed, relevant air quality standards are defined and existing conditions are characterized. Measured and simulated pollutant concentrations are compared with air quality standards. Finally, mitigation measures are proposed to insure proper air quality management inside the tunnel (Section 8.5). Tunnel emissions affect the air quality within a relative short distance from the points where emissions are dispersed, however the adjacent road network in fluences the environment in a broader area. Accordingly the air quality implications of tunnels should be examined in the context of the outside road network of which they are a part ( Section 5.1).

Other important environmental issues are noise and vibration. Noise pollution can arise during the phase of construction causing environmental hazards, because a high noise level is often generated. In addition, high volumes of vehicles during normal traffic operation can generate large noise levels, which may be above permitted levels. Increasingly, noise pollution tends to be a problem adjacent highly trafficked roadways. The strategies for noise abatement follow long-established standard procedures in the planning and construction process. Major steps forward have been made to abate noise at the source: the use of special noise-absorbing pavements can reduce it, sound insulating and sound proofing barriers have become more and more efficient, as well as the use of combined features and the deployment of improved construction machines can minimize the generation of noise and vibration ( Section 5.2). Water impact is another aspect that has to be analyzed during the life cycle of an infrastructure such as a tunnel. Detailed investigation of surface and subsurface hydrology should take place before and during construction. The least damaging route and structural elements should be chosen to get minimum interruption and alteration of hydrology patterns and processes. Drying up caused by the manner of building infrastructure is a topic which is becoming more and more important. Several studies can be carried out, which give insight into the effects of infrastructure on the hydrology of areas in the surroundings of tunnel and how to mitigate these effects. Water pollution caused by the leakage of construction materials during worksites can be reduced using containers that are designed to exclude leakage (Section 5.3).

The final objective of tunnel designers and managers is to achieve sustainable operation from both a functional and an environmental point of view, in order deliver a reasonable level of safety and to

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reduce as far as possible any negative impacts on environment. Different elements in order to improve the operational sustainability of tunnel are considered and analyzed ( Section 5.4). Contributors

This Chapter was written by Working Group 4 of the C4 committee (2008-2011) in which: 

Roberto Arditi (Italy) authored section 5.0 and coordinated the work Antoine Mos (France) and Hans Huijben (The Netherlands) authored Section "5.1 Tunnel impact on outside air quality"



Antoine Mos (France) authored Section "5.2 Noise and vibration"



 

Manuel Romana (Spain), authored Section "5.3 Water impact" Fathi Tarada (UK) reviewed the full chapter.

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5.1. Tunnel impact on outside air quality

In the field of road tunnels, air quality is traditionally considered in relation to the level of concentrations of vehicle exhaust inside a tunnel. However, the concentrations of pollutants outside a tunnel can be harmful or annoying to people. Such pollutant concentrations rapidly reduce from a portal or exhaust shaft to the surrounding environment according complex mechanisms such as the speed and direction of the wind and the neighbouring topography. Consequently, it is recognized that air quality in the vicinity of tunnel portals or other exhaust points is of interest when the traffic intensity increases and when tunnels are constructed in an urban environment. Above a tunnel, the air quality is expected to be better than if an open air road section was situated at the same location. However at the portals and shafts, polluted air is set free, when a longitudinal or transverse airflow is discharged by the piston effect of traffic and/or by ventilation systems. Depending upon background concentrations and other sources localized close to a tunnel portal or shaft, the concentration levels of pollutants can exceed the maximum levels set by authorities. In that case measures must be taken to improve the air quality in the vicinity of the tunnel. Measures may include civil or mechanical works, planning of the land use around the tunnel, etc. Most often it may be possible reduce the pollution concentrations based on operational measures such as changes in the ventilation regime. PIARC has published the Technical Report 2008 R04 "Road Tunnels: A Guide to Optimizing the Air Quality Impact upon the Environment", which focuses on outside air quality related to tunnels and it is a guide to enhancing the urban environment by altering the emissions from vehicles and changing their spatial distribution within the space surrounding a tunnel. The guide considers a wide range of design and operation opportunities to mitigate the impact of tunnels on outside air: from the selection of the most optimum location of a tunnel, to gradients, ventilation type, air discharge management, traffic management, tunnel maintenance and finally (if still useful) contaminant removal techniques.

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5.2. Noise and vibration

Noise is generally regarded as one of the key nuisances perceived by humans, which can significantly affect urban areas. It should therefore be taken into account in the design of tunnels, especially for those urban tunnels that have a high concentration of acoustical receptors in the immediate vicinity of portals and shafts. Traffic-generated noise is not specific to tunnels. Underground infrastructures are generally regarded as having a positive influence on the acoustic environment, but there might be specific issues near the portals in some configurations. In most developed countries, noise impact studies are performed for every new infrastructure project (or significant modification), and the existence of tunnels is, of course, to be taken into consideration at that stage. The main source of noise impacting the environment surrounding tunnels is the traffic. Part of the noise from vehicles running inside tunnels is reflected by the tunnel lining and reaches the portal that itself becomes a source of noise. Under certain conditions the noise level near the portal of a tunnel can be higher than the noise level of a related open air section. However, this kind of effect is significant only for those acoustic receptors lying in the immediate vicinity of the tunnel portal: moving away from the portal noise levels rapidly diminish, since the noise coming from the tunnel is attenuated by the prevailing effect of noise generated by vehicles in the open air sections. There are also sources of noise that are associated with the tunnel infrastructure, the main one of which is the ventilation system. In the case of transverse ventilation, or longitudinal ventilation with extraction shafts, fans and air flow through inlets and outlets may generate significant noise, and in some cases they have to function even at night time when noise environmental standards are set at lower targets. One solution may be to reduce the use of the ventilation system by optimising its control, but this can only be achieved to a limited extent. The most effective solution is to take these problems into account at the design stage. Considering that the most prominent noise effects are geographically limited, air inlets/outlets may be located as far away as possible from neighbouring buildings, but this may result in significant increases in cost. The air velocity should be kept at relatively low values at air inlets/outlets to reduce noise generation by making the size of these openings large enough. Additionally, silencers are most often necessary to prevent the noise generated by the fans from "leaking" out of the ventilation plant. In the case of longitudinal ventilation, the noise impact from fans on the environment is generally moderate because, on the one hand, jet fans should not be located too close to the portals for maximum efficiency (consequently the noise of fans is "diluted" within the traffic noise), and on the other hand, silencers are usually fitted to the fans to maintain an acceptable noise level inside the tunnel. However, for particularly sensitive configurations, it might be necessary to select specific designs or operational measures. Traffic-generated vibration is rarely a significant issue in the operation phase of a road tunnel (unlike rail tunnels, because trains generate much more vibration than road vehicles). Should such a problem occur, there is generally little that can be done apart from prohibiting access to the heaviest vehicles. Another source of vibration is the fans. These should be carefully balanced to avoid excessive vibration. However, fan vibration is generally not perceivable in the environment; it affects primarily the machine itself, and can compromise its longevity. It can also become a safety issue because jet fans, for example, may lose parts or even fall down from the tunnel ceiling due to excessive vibration. Vibration monitoring is crucial for the reliability and safety of jetfans. Vibration is much more problematic during the construction phase, especially when explosives are used. Tunnel construction and related environmental measures are outside the scope of the PIARC committee on road tunnel operation; specific recommendations are published by the ITA.

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5.3. Water impact

The impact of road infrastructure on water quality can be very significant during both normal operation (leaking of hydrocarbon products, tyre wear, etc.) and accidental situations (spilling of large quantities of pollutants). The existence of a tunnel does not change the problem very much. As on any road, there is a need for water treatment (decanting, removal of pollutants) before releasing it into the environment. A few tunnel-specific facts should however be taken into account when designing water management systems. First, tunnels need to be cleaned on a regular basis, as often as every month for heavily trafficked urban tunnels. This generates large amounts of waste water containing cleaning products. Second, tunnels in which dangerous goods transports are allowed are generally equipped with specific gutters in order to limit the spread of flammable liquids on the pavement. If an accidental spill occurs, the flow rate of pollutant liquid in these gutters may be higher than what is encountered on a regular road surface, and the water management system should be capable of coping with these flow rates. Very challenging issues related to water may be encountered during the construction phase in sensitive environments, for example regarding the turbidity of the construction site effluent. Appropriate measures should then be taken. In some cases, they represent significant constraints and cost for the construction works. Tunnel construction and related issues are outside the scope of the PIARC committee dedicated to road tunnel operation. The reader is therefore encouraged to consult ITA recommendations for further details. Water impact is another aspect that has to be analyzed during the life cycle of an infrastructure as tunnel. Most of the impact of tunnels on water (and water on tunnels) happens during their construction, but some of the impacts remain for a long time and can become a hindrance to the tunnel operation and maintenance. Due attention must be given to these processes during the tunnel planning and design stages, in order to avoid adverse, and costly, consequences. Detailed investigation of surface and subsurface hydrology should take place before and during construction. The least damaging route (and structural elements) should be chosen to obtain minimum interruption and alteration of hydrological patterns and processes.

Theoretically, tunnels can be: impermeable (allowing no ingress of water and developing the full water pressure on the lining) and permeable or semi-permeable (allowing some ingress of water and avoiding the development of full water pressure on the lining). In practice most tunnels are permeable during their construction and semi-permeable during their operation. Fig. 5.3.1 shows water ingress in a tunnel built with segments and designed to be impermeable.

Fig. 5.3.1 : Water ingress in a tunnel built with segments

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In non lined tunnels (or with a permeable lining) water ingress can be important. Fig. 5.3.2 shows water flowing through a permeable basalt layer in Canada.

Fig. 5.3.2 : Water flowing through a permeable basalt layer The drying up of groundwater levels caused by the manner of building infrastructure is a topic which is becoming more and more important. The effect usually does not finish during tunnel operation, and the groundwater original levels almost invariably go down, with an irreversible impact on water supply wells.

Fig. 5.3.3 : Drainage water flowing and lime calcium hydroxyls precipitating in concrete lined tunnel

Fig. 5.3.4 : Similar effect in construction joint

The water entering a tunnel can dissolve the free lime hydroxide in the concrete lining, becoming more alkaline and releasing solid deposits in the drainage systems. This effect is more frequent in old tunnels with out-dated drainage systems. Fig. 5.3.3 shows drainage water flowing and lime calcium hydroxyls precipitating in a concrete lined tunnel. Fig. 5.3.4 shows a similar effect in a construction joint.

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5.4. Sustainable tunnel operation

The current international trend is to demand from road operators and road authorities that they should promote an efficient use of energy and to adopt sustainable methods for the construction and operation of public roads. PIARC throughout its history has published several reports aiming at improving the efficiency of tunnel operations, the reduction of operating costs, and the mitigation of environmental impacts. The "sustainable tunnel operation" as a whole will be a basic topic to be dealt by PIARC during next cycle (2012-2015).

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6. GEOMETRY



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6. Geometry As mentioned extensively in the Chapter 1 "Strategic issues" of this Manual, the geometric characteristics have to be defined at the most early stage of the conception of a tunnel, and even of a road link comprising possibly one or more tunnels. These characteristics are of very different natures, and can be grouped in the following categories:   





the relation between construction method and cross-section the theoretical notions related to traffic capacity the general alignment of the road comprising the tunnel : number of carriageways and lanes, offcarriageway provisions (lateral and possibly central), headroom, maximal slopes, minimal horizontal and vertical radiuses, transverse slopes, the detailed characteristics of the transverse profile inside the tunnel : width of lanes and off-carriageway provisions, headroom taking into account the construction method and the equipment to be installed the space needs for safety features as part of the cross-section : lay-bys, emergency stopping lanes, emergency service recesses, safety fences and barriers, safety recesses, etc. the specific geometric characteristics of other features located out of the cross-section: emergency exits, evacuation galleries, by-passes, cross-connections, etc. the influence of the geometrical characteristics on safety.

This chapter is mainly based on the Technical Reports 05.11.B " Cross section geometry in Unidirectional road tunnels" and 05.12.B "Cross section design for bi-directional road tunnels" . Section 6.1 recalls the relation between construction method and cross section. Section 6.2 gives a summary of the theoretical notions related to traffic capacity. Section 6.3 recalls the main rules concerning the general alignments of roads, including the main figures used in some countries, and insists on the need to maintain the largest geometrical characteristics of the outside road in the tunnel itself (with the important exception of the maximum slope, which has to be limited). Section 6.4 deals specifically with the transverse profile of the carriageway of road tunnels, for uni- as well as bidirectional ones. Section 6.5 concerns the vertical clearance of the tunnel. Section 6.6 concerns the emergency lanes and the off-carriageway features, as well as the various safety features that have to be found along the tunnel.

Contributors

This chapter of the manual was written by Willy De Lathauwer (Belgium), associate member of C4 committee as ITA representative. Fathi Tarada (UK), reviewed this Chapter.

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6.1. Relation between construction method and cross section For road tunnels the cross sectional shape is typically rectangular or circular and depends mostly on the method of construction. In table 6.1-1 some typical cross sections and corresponding construction methods are indicated. The dimensions of the shapes employed are dependent on the dimensions of the cross section necessary for traffic. These vary due to: 1. 2. 3. 4. 5. 6.

Traffic volumes and the importance of the tunnel Design speeds, safe stopping distances and sight distances Space for in-tunnel equipment such as: signs, traffic and environment monitoring Cost of the facility balanced against the required safety standards The traffic management required to respond to an incident in the tunnel The usual local norms and the financial possibilities.

Internationally the response to the above differences varies greatly. In individual countries the response to the different situations has varied and evolves with time. N°

Cross Section

Typical Construction method

Comment

1

Circular

Tunnel Boring Machine (TBM)

Recently extended in Japan to rectangular cross section

2

Rectangular

3

Rectangular

Cut and cover tunnel

4

Horse-shoe

Blasting

5

Circular Crown and Elliptical Invert

Immersed Tube Tunnel In USA circular cross sections are common Precast technology sometimes leads to circular cross sections above the carriageway Applied in hard rock

Excavation In hard rock, horse-shoe shapes are usual sustainment methods

Table 6.1-1: Cross Sections and Typical Construction Methods

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6.2. Theoretical and practical tunnel traffic capacity The theoretical capacity of a road section is defined as the maximum through-flow of vehicles per hour. It is determined by measuring the maximum number of passenger cars in a fifteen-minute period and multiplying this by a peak hour factor. This is not an absolute maximum, but rather refers to reasonable repeatability. Expressed in this way, the capacity only depends on the number and width of lanes and off-carriageways, and the slope of the section. It does not depend on the percentage of heavy vehicles, since it is clear that this intensity will be a maximum when traffic is formed exclusively by light vehicles and regular drivers. If there is no element that limits it, this theoretical capacity is approximately 2,200 vehicles per hour per lane (v/h/l). More information is available in Chapter 4 "Capacity and speed in relation to the geometry of roads and roads tunnels" of Report 05.11.B and in Chapter 3 "Traffic speed and densities" of Report 05.12.B. The practical capacity of a section is calculated based on the theoretical capacity without the previously mentioned restrictions (2,200 v/h/l). Limiting factors are applied based on the actual characteristics of the roadway. These main factors are: 





Fw : Lane width factor, which reduces the capacity depending on the width of the lanes and the off-carriageways. It is considered that a lane does not limit the practical capacity if the width is equal to or greater than 3.60 m. Fhv : Heavy vehicle factor, which adjusts the theoretical capacity depending on the percentage of heavy vehicles and the inclination and length of the ramp or slope of the roadway. Fc : Correction factor due to the predominant type of driver. This factor adjusts the capacity based on whether the drivers are regular drivers along the route and if the type of traffic is that of a working day.

The practical capacity of a carriageway in one direction, Cp , is calculated then by: Cp= 2200 . N . F w . Fhv . Fc in which N is the number of lanes.

The factors can further be calculated and adapted according to formulas and tables given in Chapter 4 "Capacity and speed in relation to the geometry of roads and roads tunnels" of Report 05.11.B and in Chapter 3 "Traffic speed and densities" of Report 05.12.B. More information can also be found in the HCM (Highway Capacity Manual) issued by the Transportation Research Board (USA).

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6.3. General alignment of roads and national examples 6.3.1 Horizontal alignment

Small curves should be avoided, especially if they are connected to a straight alignment. A minimal curvature of 550-600 m should be observed. The lateral clearances must also allow for longitudinal visibility in curves. In urban tunnels, it should be adequate to consider design speeds close to the actual speed in fluid and uncongested traffic flow.

6.3.2 Longitudinal profile

Due to the influence on speed, longitudinal downgrade profiles cause more accidents, especially with high traffic volumes (increase of speed downwards).

6.3.3 Cross section

Reduced cross-sections are dangerous and may cause accidents. Attention should be given to the point that, if the width of the carriageway and/or off-carriageway area in the tunnel and in the approach to the tunnel is less than on the open road, these changes should be implemented well before the tunnel portal and as smoothly as possible: see Chapter 4.7 "Design of tunnel portals" of Report 2008R17.

6.3.4 Height clearance

Accidents involving oversized vehicles are often recorded in rectangular tunnels or tunnels with a ceiling for ventilation purposes. It is advised to install outside the tunnel, ahead of each portal, a signed escape route as well as a system to stop physically oversized vehicles. More information is available in Section IV.2.6 "Height clearance" of Report 05.04.B.

6.3.5 Uni- or bidirectional tunnels

Bidirectional tunnels cause more accidents than unidirectional ones. Nevertheless users observe fairly well the prohibition to overtake in tunnels with average longitudinal gradients. In case of steep gradients it should be adequate, however, to plan an additional lane for slow vehicles. It is strongly advised against changing the traffic direction to absorb daily traffic peaks. Bidirectional tunnels may be economic for the phased construction of motorway tunnels, where economic considerations require bidirectional traffic operation to be planned at a first stage, then unidirectional at a second stage. However, this is under the proviso that the usable tunnel width is designed with bidirectional traffic requirements in mind and is thus wide enough, in order to absorb a number of traffic peaks (e.g. summer or winter holidays). Even if such an arrangement may be acceptable from a safety viewpoint, it must be avoided as often as possible. For urban tunnels it must be prohibited.

6.3.6 Interchanges

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Underground interchanges (slip roads in and out) may cause accidents. They must thus be correctly designed. The lighting equipment should lay emphasis on these singular points and on the geometric challenges faced by the driver. Consideration must be given to the driver’s visual perception. Inside the tunnel, the traffic exits must be located at a distance from the portal. A number of accidents, mostly injury accidents, have occurred in tunnels where the slip road is located directly after the tunnel. In the case of tunnels with restricted space conditions, it should be adequate to plan an additional lane inside the tunnel for the exit slip road.

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6.4. Carriage way geometry The terminology has to be defined as follows: 1. Carriageway, comprising the area inside the inner edges of the outermost traffic lane markings 2. Off-carriageway, comprising those areas in plan outside the carriageway, including edge lane markings, clearances, emergency lanes, sidewalks and safety barriers.

Fig. 6.4-1 : Example of cross section More information is available in Chapter 2 "Terminology" of Report 05.11.B . To aid good management, roads are classified on a hierarchical basis according to function. Road networks of highest classification are interstate connections such as the Trans European Road Network or the Interstate Highways in the USA. National networks consist of roads that connect urban regions and national economic centres. Regional networks provide connections between regional towns. Functional requirements to the distinct functional networks or roads are formulated such as speed, congestion level, distances between intersections. Most countries have their own directives and guidelines regarding requirements to carriageway geometry. A comparison of international guidelines is given in the Chapter 5 "Traffic lanes and carriageway" of Report 05.11.B. Country and name of guidelines or other source

Design Speed or Reference Speed [km/h]

Width of Traffic Lane [m]

Austria RVS 9.232

80 - 100

3.50

0.15

7.00

Denmark (practise)

90 - 120

3.60

0.10

7.20

France CETU

80 - 100

3.50

?

7.00

100 (26T, 26Tr)

3.50

0.15

7.00

70 (26t)

3.50

0.15

7.00

110 (29.5T)

3.75

0.15

7.50

80 - 120

3.50

7.00

60

3.25

6.50

Germany Germany RAS-Q 1996 Germany RABT 94 Japan Japan Road Structure Ordinance

Width of Traffic Width of Lane Marking Carriageway [m] [m]

Fig. 6.4-2 : Comparison of international guidelines (Excerpt of table 5.1 of the Report 05.11.B) It is recommended that the width of traffic lanes in tunnels with design velocities of 100 km/h shall not be less than 3.50 m. When it is acceptable/necessary to impose speed limits (80 or even 60 km/h) in tunnels on roads (i.e. unavoidable sharp curves, noise reduction in built up area, limited capacity necessary, cost reduction) a restriction of the width of traffic lanes (for example to 3.25 m) may help

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drivers to reduce speed and thus act as a psychological support of the speed limit. This generally has to be enforced with frequent controls and high fines. In some urban tunnels, where only light vehicles are allowed, narrower lanes are accepted; in curves attention has to be given to the influence of the bending of the pavement on the width of the structure. More information is available in Chapter V "Traffic lanes and carriageway" of Report 05.11.B and Sections 7.1 to 7.5 of Chapter 7 "Geometric cross section" of Report 05.12.B .

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6.5. Vertical clearance The minimum headroom above the carriageways is at least equal to the maximum (design) height of heavy good vehicles (HGV) that are allowed on the road, with additional clearance necessary to allow for movements of the vehicles due to irregularities of the pavement and the vehicle. The minimum headroom depends on the maximum height of heavy good vehicles and varies from country to country. In most European countries the maximum height of heavy good vehicles is 4.0 m; certain countries allow higher values (UK, USA): see table 7.1 in Chapter 7 "Maintained headroom" of the Report 05.11.B. In the European Union the maximum height of heavy good vehicles is 4.00 m, although the Geneva conventions allow a maximum of 4.3 m. If a margin of 0.20 m is added to these maximum heights in order to absorb vertical movements of the HGV, the minimum vertical clearances required are 4.20 m (4.50 m). Above these minimum clearances, additional headroom is necessary for drivers of HGV's to feel comfortable. This comfort margin is related to the object distance. The minimum height plus the comfort margin yields the maintained headroom. If a value of 0.30m is taken for the comfort margin, the maintained headroom is 4.50 m (Geneva convention 4.80 m, UK 5.35 m, USA 4.90 m on freeways, 4.30 m on other highways). To prevent damage of equipment mounted above the carriageway by loose tarpaulins for instance, an additional allowance is often applied. Finally, allowance has to be made for inaccuracies in the construction, bending of the roof and possible later paving overlays see Chapter 7 "Maintained headroom" of the Report 05.11.B and Chapter 7.8 "Vertical clearances" of the Report 05.12.B. The specific case of the geometric design of reduced height urban tunnels is treated separately, as they are normally reserved to cars and some restricted categories of (light) vans. The full study has been made for France and implies the following specific points due to the presence mainly of cars, available in the article "Reduced height urban tunnels geometric design" (Routes/Roads 288 - 1995):     

slopes : higher limits are possible : § I.3, p 40 interdistance of interchanges : § II.1, p 41 definition of the height : § II.3, pp 43-44 horizontal and lateral alignment : § III.1, pp 45-46 cross-section : § III.2, pp 46-50

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6.6. Emergency lane, off-carriageway geometry and special elements To facilitate and clarify communication and comparison it is necessary to define a minimal set of terms regarding carriageway and off-carriageways. The working group which produced the Technical Report 05.11.B decided to apply the following terminology: 1. Carriageway, comprising the area inside the inner edges of the outermost traffic lane markings; 2. Off-carriageway, comprising those areas in plan outside the carriageway, including edge lane markings, clearances, emergency lanes, sidewalks and safety barriers : see graphs in Chapter 2 of the Report 05.11.B : Terminology The distinction is justified in that there appears to be general agreement about the use and dimensions of the carriageway, while the dimensions of and requirements for elements of the off-carriageway differ greatly between countries. The emergency lane is defined as an "area of hard clearance to park vehicles in case of emergency". On roads of the motorway type in the open air usually an emergency lane is provided. Hard clearances in tunnels are often restricted for economic reasons. This restriction can make it impossible for broken-down vehicles to park on the hard clearance adjacent to the driving lane without occupying part of the driving lane and thus disrupting traffic flow. The geometry of off-carriageways varies between different countries, e.g. no general rules or figures can be given. In many countries, due to costs, the width of the hard clearance is too small to park a vehicle adequately. Therefore at certain distances lay-bys are provided. However in Norwegian and Spanish experience only 40 % of the broken down vehicles effectively reach or use the lay-bys. This demonstrates that lay-bys cannot completely replace emergency lanes: see Sections 8 to 10 of Chapter III "Breakdowns" of Report 05.04.B . The hard clearance should give the possibility to park a stranded car outside the carriageway. Therefore the width measured from the outer side of the edge lane marking should be at least the width of a passenger car (1.75 m) plus a width of 0.50 m. to enable motorists to descend, resulting in a hard clearance of 2.45 m. In case also heavy trucks should be parked outside the carriageway a width of (2.50 + 0.50 + 0.20 =) 3.20 m is required as explained in Chapter 6 "The off-carriageway" of the Report 05.11.B .

Safety barriers are commonly referred to as "massive construction to guide vehicles colliding with the tunnel side-wall safely back in the direction of traffic". It differs from guard rails, which are a flexible or frangible beam type construction supported on poles to prevent vehicles colliding with the tunnel side-wall.

Figure 6.6-1 : Typical alignment of safety barriers in the off-carriageway

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In the case of tunnels it is questionable whether object distance is determined by the distance between the inner side of the edge lane marking and the kerb of walkways, the front of safety barriers or guide rails, or the tunnel side-wall. There is general agreement that in case low level walkways are employed the distance to the tunnel wall is a good measure. When no walkways are present the distance to the base or to the top level of the safety barriers has to be considered. Especially in tunnels drivers prefer a certain distance to the wall (or walkway, guide rail or safety barrier) due to smaller movements of the eye-angle when fixed on objects. Experience shows that where object distance in tunnels is smaller than on the adjoining road motorists change course to keep distance from the tunnel wall: see Chapter 6 "The off-carriageway" of the Report 05.11.B .

If vehicles crossing the edge lane marking cannot be redirected in time then the consequences of collision with the wall must be minimized. This can be achieved by means of safety barriers or guard rails. Safety barriers require less space than guard rails. When vehicles collide with safety barriers at small (acute) angles they can be guided back in the direction of traffic and there is a chance of preventing major accidents. When vehicles collide with safety barriers at large (obtuse) angles the results of the collision may be more serious. Guard rails are not as effective as safety barriers at correcting/redirecting errant vehicles; however, they cause less damage in a collision at an obtuse angle. That is why safety barriers are to be preferred in case of narrow hard clearances and guard rails in case of broad hard clearances. As guard rails require bending space this would mean extra width of the tunnel, which in many cases is not feasible from an economic point of view. Especially at restricted speed, safety barriers perform well. Moreover, barriers need less maintenance.

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ROAD TUNNELS MANUAL

7. STRUCTURAL FACILITIES RELATED TO OPERATION AND SAFETY



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7. Structural facilities related to operation and safety In addition to the basic cross-section and alignment geometry required for traffic operations, special facilities are provided in most road tunnels to cater for the particular operational and safety demands of the tunnel environment. Emergency exits are provided in all except the shortest tunnels to allow tunnel users to evacuate on foot from the traffic tube to a place of safety.The different types of emergency exits for pedestrians are considered in Section 7.1. These include cross-connections and cross-passages between tubes, refuges where the public can remain safely during an emergency, and safety galleries (passages) constructed alongside the traffic tubes or perhaps under the carriageway and leading to the surface. Section 7.2 considers the facilities provided for vehicles.These include lay-bys, turning bays and cross-connections between tubes for vehicles.These cater for situations such as vehicle breakdowns or to allow vehicles to turn around or cross into an adjacent tube, which could be useful for maintenance, for manoeuvring emergency vehicles during an incident, or for traffic management following an incident. Section 7.3 considers the geometrical aspects of safety recesses, which may be provided at intervals along the walls of a tunnel, to allow the occupants of a broken down vehicle to move away from the carriageway and minimise the risk of being struck by moving traffic. Drainage is important to minimise the size of pools that may otherwise form in the event of a spillage from a road tanker or during routine wall washing. In the event of a spillage of flammable liquid, the drainage system can have a major effect on the size of a resulting fire. Section 7.4 considers the different types of drainage systems provided in road tunnels. Section 7.5 describes other facilities that may be provided within or at the portals of a tunnel.

Contributors

This Chapter was written by Robin Hall (UK).

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7.1. Emergency exits Emergency exits are provided in all except the shortest tunnels to allow tunnel users to evacuate on foot from the traffic tube to a place of safety in an emergency. In short tunnels, the portals are adequate as emergency exits. In most tunnels, however, additional emergency exits are required in order to limit how far tunnel users have to travel to reach a place of safety. Emergency exits may be provided in different ways, including: 

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Cross-connections or cross-passages between tubes (which may be used by vehicles as well as pedestrians).In some cut and cover tunnels, the cross-connection may simply comprise a single doorway between the tubes.For bored tunnels, the tubes are usually spaced some distance apart, and cross passages (of a measurable length) are created. Exits may lead into shelters where the public can remain safely during an emergency. However these shelters have to be connected to the surface directly or by an escape gallery, in order to make possible in a second stage the escape under the control of the fire brigade. Shelters are specially equipped enclosures with a separate special fresh air supply and an emergency telephone. Some welfare facilities may be provided. The psychological effects associated with the use of shelters should be considered in the design and the procedures for their use (see Report 2008R17 "Human factors and road tunnel safety regarding users" ). Safety galleries (passages) constructed alongside the traffic tubes or perhaps under the carriageway and leading to the surface or other safe place. Escape passages leading directly from an emergency exit doorway to the surface or other safe place.Such passages are generally feasible only for tunnels with little cover (cut and cover tunnels for instance).

Figure 7.1-1 shows a typical escape pattern for a uni-directional tunnel with longitudinal ventilation.

Fig. 7.1-1 : Typical escape pattern for uni-directional tunnel with longitudinal ventilation The appropriate spacing between emergency exits depends on:   

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types of vehicles using the tunnel, which dictates the nature of incidents that could occur; traffic volume and the number of tunnel users that may need to use the exits; the capability of tunnel ventilation system to maintain tenable conditions for evacuation in the tunnel; incident detection and warning systems; the nature of the protected routes beyond the emergency exits (including their dimensions and the presence of significant gradients or stairs); and

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human behaviour.

The optimal distance between two emergency exits is generally estimated to be between 100 and 500 m. The following design principles are important: 

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emergency exits should be clearly signed as such to distinguish them from equipment room access. The recommended colour of the doors (very often the "emergency exit" colour green) must be considered in combination with the type of tunnel lighting; doors and openings should be sized to handle a large number of people in a short time as well as the passage of rescue workers with equipment or stretchers; emergency exits should be visible either directly or by visible and recognisable signs from any position in the tunnel; the luminance of access floors, doorsteps, etc. and the room just behind the emergency exit should be "inviting" and be designed to prevent people from falling or stumbling; curb lighting/markers should not be obstacles for walking people; emergency exit doors should not be locked.

Figure 7.1-2 shows a possible design of an emergency exit.

Fig. 7.1-2 : Design of an emergency exit (Mont Blanc tunnel : France - Italy) Further discussion of emergency exits is provided in the Technical Report 1999 05.05.B "Fire and smoke control in road tunnels" and, in more detail, in the more recent Technical Report 2007 05.16.B "Systems and equipment for fire and smoke control in road tunnels" .

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7.2. Facilities for vehicles The large majority of road tunnels have no emergency lane. This creates a likelihood that tailbacks can occur - depending on the traffic intensity, the presence of broken down vehicles or other problems causing drivers to stop. According to some German and French statistics, tunnels without emergency lanes are less safe than tunnels with emergency lanes (see Technical Report 2008R17: "Human factors and road tunnel safety regarding users"). Lay-bys allow vehicles to stop in a tunnel without blocking the carriageway.This reduces traffic disruption and the risk of a collision.It is easier and safer for the occupants to get out of their vehicle in a lay-by, for example in order to use an emergency telephone.The shelter from traffic can be particularly beneficial for disabled drivers.Lay-bys are also very important for the maintenance of the tunnel and ensure the safe parking of the maintenance vehicles. The distances between lay-bys vary from tunnel to tunnel. In some national guidelines these distances depend on the classification of the roads the tunnels form part of the Technical Report 1995 05.04.B "Road safety in tunnels" noted that their utilisation rate was generally low. In tunnels with lay-bys, only 20% of faulty vehicles stopped in a lay-by.Recommendations were given to improve this. In longer tunnels, facilities may also be provided to allow vehicles to turn around or cross into an adjacent tube.These could be useful for maintenance, for manoeuvring emergency vehicles during an incident, or for traffic management following an incident.More specifically, some countries provide turning bays for vehicles. This is because, although cars and vans can turn easily at standard lay-bys, heavy goods vehicles and buses require more space. These turning bays usually measure 4 m by 17 m or larger (see the Technical Report 1999 05.05.B: "Fire and Smoke Control in Road Tunnels" ). When they are provided, they should be located every 1-2 kilometres.

Fig. 7.2 : Example of turning gallery

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7.3. Safety recesses Most road tunnels have emergency stations located at intervals along their length, typically equipped with emergency telephones and portable fire extinguishers (and sometimes fire hoses), to be used by tunnel users in case of breakdowns or incidents. There is great variety in the housing and location of these emergency stations, ranging from simple boxes attached to the tunnel wall to recesses or rooms with or without doors for separation from the traffic tubes.Recesses allow the occupants of broken down vehicles to move away from the carriageway and minimise the risk of being struck by moving traffic. To prevent feelings of claustrophobia within enclosed emergency stations the use of appropriately specified glass door panes is recommended. A good alternative is to avoid doors and to guarantee good voice communication by means of noise cancellation technology. The Technical Report 2008R17: "Human factors and road tunnel safety regarding users" considers the human factors associated with the design of such facilities, which need to be highly conspicuous and identified by clear signs. The equipment provided at emergency stations is discussed in Chapter 8.

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7.4. Tunnel drainage Road tunnels are equipped with a drainage system to deal with surface water from portals, groundwater infiltration through the lining, wall washing water, spillages from a road tanker and fire fighting water. Where the transport of dangerous goods is permitted, the drainage of flammable and toxic liquids is a key concern. Drainage is important to minimise the size of pools that may otherwise form in the event of a spillage from a road tanker. In the event of a spillage of flammable liquid, the drainage system can have a major effect on the size of a resulting fire. Drainage systems typically consist of gulleys, channels, pipes, sump and pumps, oil/water separators and control systems for collection, storage, separation and disposal of effluent that might otherwise collect on the roadway. Some authorities specify the use of slot gutters in order to maximise drainage performance. Sump and pumps are generally provided at the portals and at low points. The impact of water on tunnel construction and operations is discussed in Section 5.3. Fig. 7.4-1: Example of a mid tunnel sump and pumps

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7.5. Other facilities Other structures may be provided within or at the portals of a tunnel are described below.

7.5.1. Emergency recesses

Emergency or fire-fighting recesses contain fire hydrants, hose reels (sometimes) and special equipment for use by the fire brigade. They are located at intervals along the tunnel length. They may be combined with the safety recesses, containing emergency telephones and portable fire extinguishers, discussed in Section 7.3.

Fig. 7.5.1-1 : Example of an emergency recess

7.5.2. Plant rooms within a tunnel

In many tunnels, electrical substations and mechanical, electrical, communications and control equipment may be housed in plant rooms located within the tunnel. The layout and sizing of plant rooms follow the same principles as for plant rooms in service buildings. For example, adequate space is needed for opening of cabinet doors and access to switchgear. Allowance for cable runs and bend radii is important and can be more problematic compared to external buildings because of tunnel construction and space constraints in the tunnel bore.

Fig. 7.5.2-1 : Example of a tunnel plant room

Consideration should be given to safe access to tunnel plant rooms This may be possible during bore closures only. In some tunnels, lay-bys may be provided adjacent to plant rooms to allow maintenance vehicles to stop safely, even without tunnel closure.

7.5.3. Splitter walls

Between the exit portal and the neighbouring entry portal of two uni-directionally used tubes, a substantial air recirculation may take place, depending on the local geometry and wind direction. The same problem exists between exit portal and fresh air intake of a semi-transverse ventilation station.

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In short tunnels with high self-ventilation this may be of no concern, but in longer tunnels this effect should be reduced. Depending on the circumstances, the splitter wall may need to extend approximately 20 to 40 m from the portal. Further details are given in Section IV.2.3 "Recirculation" of report 1995 05.02.B "Road tunnels emissions, environment, ventilation".

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8. EQUIPMENT AND SYSTEMS



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8. Equipment and systems If tunnels are longer than a few hundred metres, specific equipment is required to enhance safety to the users, both in normal situations and in case of accidents. To reduce the risks of accidents and limit the possible consequences, but also to keep an adequate level of comfort to the users, a large variety of equipment can be installed. Chapter 7 of the report 05.06.B "Reduction of operating costs of road tunnels" discusses road tunnel equipment and Chapter 3 of the report 2008R15 "Urban road tunnels" provides details for the design and refurbishment of equipment. A significant amount of electric power is required to feed the equipment installed in the tunnel. The electrical power supply systems (Section 8.1) must provide enough power in the case of normal and emergency conditions. This also means that the system must work even in the case of blackouts, in order to feed at least the equipment which is absolutely necessary. The status of this equipment should also be monitored. For this reason, a SCADA sys tem (Section 8.2) may be implemented. A first type of equipment is the communication and alert systems (Section 8.3). This includes systems used to check periodically the conditions in the tunnel and also to make the operator aware of a possible danger or an accident. Together with systems for surveillance and control of traffic (Section 8.8), some detection systems can be installed. These include automatic incident detection and smoke/fire detection. This information may also come directly from people involved, through alarm push button or emergency telephones. The latter also allows a communication between people in the tunnel and control personnel. This is useful for the control personnel to have additional information with respect to locations, status of people, etc. but also to supply information to people in the tunnel. This kind of equipment also includes systems used to alert the users in the tunnel or to coordinate the intervention. Loudspeakers and radio-retransmission of public FM broadcasts, frequencies of operators and emergency services can be used for these purposes. To guarantee comfort to the users and reduce the risks of accident it is important to obtain adequate visibility and reduced concentration of contaminants. For these purposes, an adequate lighting system (Section 8.4) and ventilation system (Section 8.5) are necessary. Ventilation is also crucial in the case of emergency conditions, as it affects both the fire development and smoke propagation. Depending on the traffic and the tunnel length the ventilation can be only natural, only mechanical or mixed natural/mechanical (i.e. natural in ordinary conditions and mechanical in emergency conditions). An additional element to manage risk is signalling (Section 8.9). This is important in order to highlight possible obstacles or danger, but also to help finding the emergency exits, alarm pushbutton, extinguishers, etc. In the case of accidents, equipment is required to extinguish fire. This includes fire-fighting equipment available in the tunnel to the users and the emergency teams ( Section 8.6) and fixed fire fighting systems (Section 8.7), which automatically intervene. In these conditions, barriers ( Section 8.10) are important to prevent users outside the tunnel at the time of accident from entering the tunnel.

Contributors

This Chapter was written by Working Group 1 and Working Group 4 of the C4 committee (20082011) in which:   

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Antonio Valente (Italy) coordinated the work Jean-Claude Martin (France) authored Sections 8.0, 8.1 and 8.2 Arthur Kabuya (WG4 : Belgium) and Jean-Claude Martin (France) authored Section 8.3 excepts Sections 8.3.4. Automatic incident detection and 8.3.5. Fire/smoke detection : Purpose of fire and smoke detection that were authored by Arthur Kabuya (WG4 : Belgium) Jean-Claude MARTIN (France) authored Section 8.4 Antoine Mos (WG4 : France) authored section 8.5 Ventilation Art Bendelius (WG4 : USA), authored Section 8.6 Fire fighting equipment

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Arnold Dix (WG4 : Australia) and Fathi Tarada (WG4 : UK) authored Section 8.7 Fixed fire fighting systems Jean-Claude MARTIN (France) authored Sections 8.8, 8.9 and 8.10 Fathi Tarada (UK) and Ignacio del Rey (Spain) coordinated and reviewed the WG4 inputs Jean-Claude MARTIN (France) coordinated and reviewed the WG1 inputs Fathi Tarada (UK) reviewed the EN version.

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8.1. Electrical power supply Most of the tunnel equipment and systems requires electrical energy to operate. Therefore, equipment for supplying power to the tunnel must be installed. This installation has to satisfy two essential requirements:  

Supply safe and sufficient power to allow all the equipment to operate Meet the needs under all operational situations (normal, degraded, critical).

The power required for supplying a tunnel is directly related to the nature and number of equipment installed in it. Depending on the amount of electrical energy required (kWh), power may be supplied in low voltage or high voltage. Each country has its own regulatory requirements with regard to tunnels and a specific structure in terms of distribution networks: therefore, the architectures retained may be significantly different in tunnels with similar characteristics. However, some identical principles can be noted, such as:  

The presence of a standby power supply (double supply, diesel generator, etc.), The installation of a device allowing remedying a total loss of power supply. This system (uninterruptible power supply (UPS), diesel generator...) supplies electricity to equipment critical for safety, during a limited period of time.

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8.2. Supervisory Control And Data Acquisition systems (SCADA) In a road tunnel, the equipment plays a vital role for the safety users. The operator therefore has to monitor such equipment continuously for determining their status (working or fault) and/or their operating mode (automatic, manual or s topped). Many devices are servo-controlled by sensors and operate automatically (lighting, ventilation...) according to pre-determined thresholds. Others are activated or deactivated depending on the operating conditions. It is thus useful for the operator to be able to remote control them (signalling, variable message signs, barriers, ventilation, lighting, pumps ...). Lastly, since the equipment may be operated very differently (continuous, occasional, or very rare), it is necessary for the operator to have information on the operational duration (hour used) for each of them. These functions of surveillance, control-command and data archiving are very often performed by a single system: the Supervisory Control And Data Acquisition system (SCADA). Several SCADA systems are available worldwide and their performance is being improved constantly. The systems installed in road tunnels of comparable characteristics are therefore rarely completely identical, even for the tunnels of the same operator. Even so, the architectures follow certain rules that are widely prevalent:    

Collection of information via networks in loop Intelligence (programmable logic control notably) installed near the equipment Separation of networks: acquisition, transport and supervision Redundancy of certain sub-assemblies for improving their dependability.

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8.3. Communication and alert systems It is important for the operator to be able to communicate with the user. It should be possible for this communication to take place in both directions - operator to user and user to operator. These exchanges should be possible in all operational situations: normal, degraded or critical. Several devices allow ensuring this communication function (the alert is considered as a particular form of communication). They do not all offer the same functionalities: some of them allow establishing a transmission from user to operator (alarm pushbuttons, automatic alarm while using certain evacuation systems ...) while others allow a transmission from operator to user (messages broadcast on FM frequencies, loudspeakers). Only one of them allows a full exchange (emergency telephones).

8.3.1. Emergency telephones

Emergency telephones allow a user, victim of an accident in tunnel, to contact the control-command centre in charge of the tunnel. In addition to establishing a voice link, the use of an emergency telephone by a user also gives his precise location. These emergency telephones are installed at fixed intervals on boxes or in emergency stations of different types. The distance between two emergency telephones is often specified by regulations and therefore varies from one country to another. The structure of this device is quite simple. The emergency telephones in the tunnel are connected to a centre that receives the calls made from the tunnel. Usually, this centre is located in the controlcommand centre of the tunnel and sometimes in the premises of police services under whose jurisdiction the tunnel is placed.

8.3.2. Alarm pushbuttons

Alarm pushbuttons allow a user to send an alarm to the control-command centre in case of accident in tunnel. Being not very expensive equipment, it can be installed at frequent intervals. This device is not much used because to a certain extent, it duplicates the emergency telephone and moreover, it does not allow a two-way communication between the user and the control-command centre.

8.3.3. Automatic alarm when emergency systems meant for users are used

As mentioned above, the user has access to several devices that he can use in tunnel, particularly in emergencies: emergency telephones and sometimes alarm pushbuttons. He also has fire extinguishers and, in most tunnels, emergency exits. It is essential for the operator to be informed as early as possible when a user operates one of these devices, in order to take adequate actions. This is not difficult when emergency telephone and the alarm pushbuttons are installed because, very often, the control-command centre receives the call or the alarm information. When the emergency telephones are terminated in a place other than the control-command centre, procedures have to be set up so that the service receiving the call informs the control-command centre at once. In the case of extinguishers and emergency exits, sensors are very often installed for detecting a change of status and communicating this information to the control-command centre by using the SCADA system. The operator is then informed that a user in tunnel is requesting assistance. For the fire extinguishers, the information taken into account is often the action of removing the equipment from its support or opening the door in the emergency station etc. For the exits, the

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information taken into account may be the opening of the door or the detection of a presence in the exit or both of these.

8.3.4. Automatic incident detection

When a tunnel is equipped with a video-surveillance system (refer Section 8.8), the images coming from the tunnel and its vicinity are shown by displays installed in the control-command centre. It is difficult for the operator to monitor more than a few displays simultaneously with a constant alertness during several hours. For remedying this difficulty, operators are increasingly using automatic systems for detecting an incident. In certain countries, the use of such equipment is even obligatory for specific tunnels. Type and Function of Automatic Incident Detection Automatic incident detection (AID) is normally based on computer-based analysis of video image streams generated from cameras set up to view tunnel traffic. A number of algorithms are available which can detect a range of incidents, including:         

stopped vehicles vehicles moving in the wrong direction speed drop slow vehicle pedestrians debris in road tunnel smoke flames entry into restricted zones

Since serious vehicle fires normally develop after traffic has stopped (e.g. following an accident), it follows that a'stopped vehicle' alarm from an AID system can be expected to precede alarms triggered by other systems, such as temperature and smoke detectors. This early warning provided by AID allows time for tunnel operators to confirm the nature and location of the incident, and to allow effective intervention., This may be through the choice of an optimal choice of ventilation configuration, prevention of secondary accidents through operational measures, rapid warning to motorists upstream of the incident. It also gives opportunity to call the emergency services, closing of access, messages on variable message signs and on the radio, call to breakdown lorry, advice to exit the tunnel, etc. Video smoke detection systems are described in Section 6.3.3 "Currently Used Methods" of report 05.16.B 2006. Video-based AID systems can provide real-time information on the traffic flow, volume and speed. They can record pictures at the origin of the incident and can interact with other systems such as the Supervisory Control and Data Acquisition (SCADA) system. Video-based AID systems normally include cameras, a video image processing system processing images from one or several cameras, Internet Protocol (IP) video encoders and decoders on IP to return images to monitors or computer displays. Furthermore a video management system composed of one or two redundant servers providing video and othersfunctions (recording of video mass and AID incident, collecting and storing real-time traffic data and traffic events, interfacing with the tunnel SCADA system), network equipment and communications lines(optical fibres, coaxial and Unshielded Twisted Pair cables). Design and Commissioning of AID Systems The design of AID systems in tunnels should be undertaken with due account of the following issues:   

Choice of incidents to be detected Detection accuracy (i.e. minimisation'false negatives' in detection incidents) Minimisation of false alarms (i.e. minimisation of'false positives')


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Location of existing cameras in the tunnel Geometric features of the tunnel Access for maintenance staff Bright sunlight'bleaching' near portals Sunlight movements in the vicinity of portals Changes caused by the passage of vehicles in the tunnel (lights, occlusion by high vehicles) Change of lighting regime in the tunnel (lighting on/off) Reflections in the tunnel In case of an AID system integrating IP video stream, the capacity of the existing IP network should be checked to ensure there is sufficient bandwidth available

The 2009 Routes/Roads article "Fire Detection Systems in Road Tunnels - Lessons Learnt from the International Research Project" concluded that "to deal with obstructions, most manufacturers of field of view detectors recommend two detectors covering the same area from different angles, such as from both directions within a tunnel". Multiple cameras may also be required for redundancy purposes, in case of camera failure. Typically, the camera fields of view are designed to overlap, such that failure of any one camera can be compensated through the images from neighbouring cameras. Section IV.2.1. "Traffic Incident Detection Devices" of report 05.15.B 2004 suggests that camera locations can vary from 30 to 150 meters if they are used for automatic incident detection. The performance of an AID system performance depends to a great extent on successful commissioning and calibration, prior to deployment. Experience from tunnel installations indicates that such commissioning and calibration can take several months to undertake.

8.3.5. Fire/smoke detection : Purpose of fire and smoke detection

Fire and smoke detectors are always an integral part of a control loop which is set up by sensors, alarm triggering equipment, transmission cabling, evaluation units, etc., and which taken together are generally referred to as a fire alarm system. Fire and smoke alarm systems in road tunnels are designed to detect fires and smoke production as fast as possible so that safety equipment and procedures can be activated without delay. Their main objectives should be: 

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informing tunnel users at the earliest opportunity so to enable them to organize their selfevacuation and self-rescuing; passing on all the possible fire parameters to the operational tunnel staff in order to enable them to change ongoing tunnel operations (traffic control and ventilation systems) according to the emergency procedures (so-called fire mode), and to call in the rescue services, medical staff, fire brigade, police, etc. to identify the locations of the fire or incident, in order to direct rescue service resources to the appropriate places to assist motorists, for example.

Principles of fire detection Basically, the fire detection principles are based on the perceived parameters determined by the fire i.e. heat, smoke, radiation and production of typical chemical substances. Therefore, the fire detecting sensors can be classified as : 

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Heat detectors : all material the characteristics of which are sensitive to an increase of heat energy whenever this implies a temperature rise. Examples are sensors which measure temperature differences with a reference temperature or rate of temperature rise, glass-fibre cables where its light transmission characteristics are a function of temperature, linear sensor cable with built in electronic circuit, etc.; Flame detectors based on their sensitivity of infrared and/or ultraviolet wavelength spectrum; Smoke detectors which measure the extinction of a infrared light beam through CO and CO 2 ionisation areas;


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Detectors which combine different types of sensors.

Each of these detectors has their own specific application domain, related to its response time, robustness, reliability, etc. Recently video AID systems have proven to be very efficient and fast in detecting fires. In fact, they detect incident any object or vehicle which does not conform to the normal expected traffic stream. The cameras can be automatically turned towards the incident scene, which enables the operator to discover the very early start of a fire. Fire/smoke detection systems are described in Section 6.3 "Fire detection" of the report 2006 05.16.B . Requirements for Fire detection system In a general way, fire detectors in road tunnels must be designed to withstand the following environmental conditions: air velocities up to 10 m/s, reduced visibility resulting from diesel exhaust fumes and abrasive wear stemming from tires and the road surface, increased and short-term fluctuating concentrations of pollutants (carbon monoxide (CO), carbon dioxide (CO2), nitrogen oxides and hydrocarbons), changing headlight intensities, engine heat and hot fumes vehicle exhaust gases, electromagnetic interferences, mixed vehicular traffic (i.e., cars, small lorries, heavy load lorries, buses and tankers) that will result in varying degrees of tunnel cross section obstruction. It cannot be stressed enough that they must have a high degree of fail-safe operation and be able to locate the fire as close as possible. It is advisable that the systems of fire detection possess certain level of intelligence to avoid false alarms, because false alarms could entail significant expense to rectify and even worse, may discourage the operators after a while run from paying attention to the alarms. Furthermore, it is imperative that the fire detection/alarm installation is reasonably priced, has low operating costs and simple to maintain: refer Section 6.3 "Fire detection" of the report 2006 05.16.B . Parameters dictated by Codes and Standards The following parameters for automatic fire detectors are specified in national and international codes and standards : maximum time for a fire to be detected, determination of the fire site location, minimum fire load to be detected, approved detection methods, assembly points for fire alarms, details pertaining to which tunnels should be provided with automatic fire alarm installations (e.g. length of tunnel, tunnels with mechanical ventilation, tunnels that are not permanently monitored by personnel, short tunnels with particularly high traffic densities). A list of detailed reference material regarding fire detector parameters are described in codes and can be found in Section 10 "References" of the report 2006 05.16.B . Fire/smoke detectors currently in use The efficiency of fire detection is not only based on the type of devices (temperature, light beam extinction, ionisation, etc.), but also on the detection strategy which and been developed, which includes the number of sensors and their level of surveillance in the tunnel. Automatic incidents detection, analysis of video images including AID systems, closed-circuit television (CCTV) observation, equipment such as fire extinguishers which activate alarms by the removal, as well as the emergency telephones are generally good means to raise an alarm. Many detectors in use are based on heat and on the rate of temperature rise. When well calibrated, this type of system generates only few false alarms, but may have a slow reaction rate. Detectors based on smoke obscuration give early signals but have suffer more false alarms because of smoke exhaust from diesel vehicles: refer to Section VI.3.1 "Fire detection" of report 05.05.B 1999 . The 2009 Routes/Roads article "Fire Detection Systems in Road Tunnels - Lessons Learnt from the International Research Project" deals with fire/smoke systems of road tunnels such as linear detection of the heat, optical detection of flames, detection by video imaging, punctual detection of heat and


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smoke detection by air sampling system. It concludes that the system of air sampling gives a good performance in terms of response time and ability to accurately locate and monitor a fire and the effect on road environment, when taking into account overall performance including false alarms, maintenance and fire detection. The information from this study can be used to determine the most appropriate technology for tunnel fire detection.

8.3.6. Radio-retransmission of public FM broadcasts, frequencies of operators and emergency services

A tunnel is a closed and confined space that very often does not allow the propagation of radio waves from broadcasters outside the tunnel. For re-establishing this propagation, it is necessary to install the equipment that allows the retransmission of the needed frequencies. Several types of services can be retransmitted:     

Rescue services (fire brigade, police...) Operator (patrols, maintenance crews, taxis, bus companies ...) Public FM broadcasts Public DAB broadcasts (Digital Audio Broadcasting) Cell phones.

There are a very large number of services whose frequencies can be retransmitted but they are not all of them covered, because of problems of cost, not to mention feasibility. As a general rule, one can find certain frequencies used by the rescue services, frequencies used by the operator, a few FM and or DAB frequencies and frequencies of cell phone operators. When one or more Radio frequencies are retransmitted, a device is installed that allows inserting prerecorded messages. In case of need, these radio broadcasters are interrupted and messages regarding the tunnel are broadcasted for the attention of users, in order to give them indications regarding the steps the operator wants them to follow. A radio-retransmission installation in tunnel is essentially composed of:  

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An antenna A transmission/reception unit that allows transmitting from the outside into the tunnels technical room that needs to be cooled. A transmission/reception unit that allows transmitting from the tunnel to the outside (not for public broadcasters but for emergency services etc.) A radiating unit in tunnel (radiating cables or antennas).

8.3.7. Loudspeakers

There are not many devices that allow addressing the user directly for giving information or asking the tunnel users to behave in a particular manner. For solving this problem, some tunnels are equipped with loudspeakers. In practice, depending on how they are used, the loudspeakers offer different functionalities. The following points can be mentioned in particular: 

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Loudspeakers installed at fixed intervals in the tunnel, to give information and instructions to users whose vehicle has stopped inside the tunnel Loudspeakers (or sirens) installed at fixed intervals inside the tunnel that emit a sound signal indicating a danger Loudspeakers (or sound beacons) installed near emergency exits that providing information to users about to use an exit and where it is located.

These devices are not however widely used at present. Their use must be studied for each case and often, they are suited for very specific tunnels (very dense traffic, length, etc.).


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8.4. Lighting In the majority of tunnels the natural penetration of light does not allow satisfactory conditions of visibility for the users. It is therefore necessary to install artificial lighting offering satisfactory conditions of visibility and comfort to the users. In terms of functionalities, the lighting installation must allow for:  

A normal lighting that provides appropriate visibility to the users, day and night A standby lighting that provides minimum visibility to the users for allowing them to leave the tunnel in their vehicles in case of power outage.

A lighting installation should be designed respecting several criteria, notably those relating to:    

Level of luminosity and lighting on the pavement Level of luminosity and lighting on the side walls and columns Values of uniformity for the different operating regimens Values of glare.

Several types of installations are possible; the most common are symmetrical lighting and counterflow lighting. Depending on the characteristics of the tunnel and the objectives defined, the lighting fittings may be installed in one or more lines, above the road, on top of walls of the tunnel...

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8.5. Ventilation Ventilation in tunnels has two functions: 



In normal operation, it ensures sufficient air quality in the tunnel, generally by diluting pollutants; In a fire situation, it should make the environment as safe as possible to the tunnel users and rescue services by controlling the flow of smoke in an appropriate way : see Sections 1.6 & 1.7 of the Report 05.16.B : "Role of the ventilation system during the self-evacuation phase" and "Role of the ventilation system during the fire-fighting phase" .

Historically, the first reason for installing ventilation systems in tunnels was the reduction of pollution levels. Although the emissions of pollutants by road vehicles have decreased dramatically over the last decades, this function is still important and must be paid close attention at the design stage. In some cases, natural ventilation due to the piston effect of moving vehicles may be sufficient to fulfil the air quality requirements in normal operation. The need for a mechanical ventilation system is assessed considering the length of the tunnel and the traffic type (bidirectional or unidirectional) and conditions (possibility of congestion) : see Technical Report 2004 05.14.B : Road tunnels: Vehicle emissions and air demand for ventilation. ventilation . This report will be replaced by a new report to be published soon. The same factors determine the requirements for ventilation in emergency situations, especially fire. The presence of other equipment or facilities, emergency exits for example, should also be taken into account. Natural ventilation might be sufficient in some cases, but mechanical ventilation is often required for tunnels over a few hundred meters in length. Different ventilation strategies may be used in tunnels. The choice between them is generally guided essentially by fire safety considerations; the use of the system in normal operation is adjusted to suit : see Chapter V "Ventilation for fire and smoke control" of report 05.05.B 1999 The longitudinal strategy consists in creating a longitudinal air flow in the tunnel, in order to push all the smoke produced by a burning vehicle on one side of the fire. If users are present on that side, they may be affected by the toxic gases and reduced visibility, so the use of this strategy in bidirectional and/or congested tunnels requires great caution. The minimum air velocity for successful smoke control depends on the design fire size and tunnel geometry (slope, cross-sectional area). The transverse strategy takes advantage of the buoyancy of fire smoke: smoke tends to concentrate in the upper part of the tunnel space, from where it can be mechanically extracted. The system is designed so as to preserve a fresh air layer in the lower part of the cross-section (correct visibility, low toxicity) which allows self-evacuation. It is therefore important to keep the longitudinal air flow as low as possible in the fire region to avoid de-stratification and excessive longitudinal spread of smoke. This strategy is applicable to any tunnel, but the design, construction and operation of the system are more difficult and expensive. The ventilation design process includes the computation of the minimum acceptable capacity of the system in terms of thrust and/or flow rates, the design of the ventilation network and the choice of appropriate ventilation equipment Chapter 4 of the Report 2006 05.16.B : Ventilation Ventilation and its appendices 12.3 "Jet Fan calculation procedure", procedure" , 12.4. "Smoke dampers" and dampers" and 12.6. "Sound impact of jet-fans".. Ventilation equipment should meet a number of specifications, including resistance to fire jet-fans" and acoustic performance. The design of appropriate ventilation control scenarios for each possible fire situation is a very important part of the process : see Technical Report 2011 R02 : Road tunnels: Operational strategies for ventilation. These scenarios can be simple, especially when the longitudinal strategy is applied, or involve a large number of measurement and ventilation devices in complex, transverse-ventilated tunnels. The optimisation of ventilation control for air quality considerations during normal operation is crucial to reduce energy consumption; it is an important issue since this consumption represents a significant part of the operational cost of a tunnel.

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The interactions of the ventilation system design with other elements of a tunnel are numerous and diverse. In the case of transverse ventilation, for example, the required flow rates may impact the excavated section, with a potentially important impact on the construction cost. Ventilation also accounts for a large part of a tunnel's power supply requirements. It interacts closely with other safety equipment such as fire detection and fire fighting systems : see Chapter 5 "Fixed fire fighting systems in the context of tunnel safety systems" of the Report 2008 R07 . The environmental issues linked to ventilation, besides the energy consumption and the related carbon footprint, are linked to the localised, concentrated discharge of polluted air from the portals and stacks. Reducing their impact on the tunnel surroundings is part of good environmental design : see Section 4.3. "Tunnel air dispersion technique" technique",, Section 4.6. "Operational aspects" and aspects" and Appendix D. "Overview of dispersion modeling in designing ventilation systems" of the Report 2008 R04. Finally, other parts of a tunnel than the main traffic space may require ventilation, most notably the emergency exits : see Section 5.3. "Escape route design" of report 05.16.B 2006 .

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8.6. Fire-fighting equipment for the users and emergency teams 8.6.1. Objectives

The primary objective of fire fighting equipment in a road tunnel is to provide the means to fight a fire within the tunnel with minimum impact on the users, the emergency responders and the structure. The World Road Association (PIARC) has addressed the systems required for the fighting of fires in road tunnels in numerous publications. This has been primarily in two publications; Technical Report 05.05.B 1999 "Fire and Smoke Control in Road Tunnels" and Technical Report 05.16.B 2007 "Systems and Equipment for Fire and Smoke Control in Road Tunnels" . In addition these issues were also covered in several Committee Reports to World Road Congresses specifically those held in Vienna (1979), Sydney (1983), Brussels (1987), and Marrakesh (2001). The systems critical to the ability to fight a fire within a road tunnel include: detection, alarm, radio communications, emergency telephone, closed circuit television, loudspeakers, water supply and distribution, fixed fire fighting, portable fire extinguishers and emergency ventilation. These systems must be planned, evaluated, designed and installed in a careful thorough integrated manner to assure that the systems are truly compatible and that the fire life safety of the tunnel is not being compromised or being over provided. Many of these elements of the tunnel fire fighting systems are addressed in other chapters of this manual. The systems included in other chapters provide detection ( Section 8.3.5), fixed fire fighting (Section 8.7), fire alarms (Section 8.3), emergency telephones (Section 8.3.1), closed circuit television (Section 8.2), loudspeakers (Section 8.3.7), radio communications (Section 8.3), emergency ventilation (Section 8.5). The systems addressed in this section relate to those systems provided for fire fighting in road tunnels by the users (motorists), the operating agency and the fire brigade. These include systems designed to furnish a supply of water through a fire line (standpipe) and fire hydrants (hose valves) and it they include the installation of portable fire extinguishers within the road tunnel.

8.6.2. Water supply

A water supply system, including water mains, fire lines or standpipes, is required to provide water for fire fighting within the tunnel (through hydrants or hose valves) and to possibly provide water for a fixed fire fighting system (Section 8.7) if installed in the tunnel (see Section VI.3.3 "Water supply" of report 05.05.B 1999). The source of water can be from a water distribution system or from a water tank.The required system pressure must match the requirements of the responding fire brigade.

8.6.3. Fire hydrants

Fire hydrants (hose valves) are required within the road tunnel to provide a point of connection for the Fire Brigade to attach fire hose and gain access to the water supply. The hydrants should be installed at regular interval spacing within the tunnel (see Section VI.3.3 "Water supply" of report 05.05.B 1999).The hydrant connections must be compatible with the responding local fire brigade(s).

8.6.4. Portable fire extinguishers

Portable fire extinguishers are provided at regular intervals within road tunnels to allow the (motorists) and operating personnel to fight a modest size fire within the tunnel prior to the arrival of the fire services (see Section VI.3.2 "Fire extinguishers" of report 05.05.B 1999 ).

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8.6.5. Fire hose

Fire hose reels are installed in road tunnels in some countries, however this is not a universal trend as other countries allow the fire brigade to bring their own hose into the tunnel for each incident (see Section VI.3.3 "Water supply" of report 05.05.B 1999 ).

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8.7. Fixed Fire Fighting Systems The Technical Report 2008 R07 "Road Tunnels: An Assessment of Fixed Fire Fighting Systems" summarises the World Road Association's views on Fixed Fire Fighting Systems (FFFS), and its recommendations pertaining to the applicability, selection and operation of such systems. In a rapidly developing fire, smoke can quickly compromise the ability of users to self-rescue, while rapidly elevating temperatures can make the tunnel untenable and destroy safety systems. An FFFS has the potential to reduce the rates of fire growth and spread, thereby assisting the safety of motorists and the emergency services during the self-rescue and assisted-rescue phases of a fire. Other potential benefits of an FFFS are the protection of the tunnel assets from fire damage, and to avoid or reduce the road network interruptions that may occur while a tunnel is being repaired following a fire incident. Except where the installation of an FFFS is prescribed by a country's tunnel design guidelines, the following steps are recommended to support the decision as to whether such a system should be installed:   

a feasibility study, a risk analysis as outlined in the European Directive 2004/54/EC; a cost-benefit analysis.

FFFS must be considered in the context of other critical safety systems such as ventilation. Rapid and accurate incident detection and FFFS response are essential components to achieve the best possible FFFS performance. The operational performance of FFFS can best be assessed through a system engineering approach, including appropriate regimes for maintenance, testing and training. Careful consideration must be made with respect to the effects of such systems on operational procedures and maintenance budgets Water-based deluge systems are by far the most common type of FFFS installed in tunnels at present. Both low-pressure and high-pressure systems are available, with the latter having smaller droplet sizes. Other water-based systems, including foam systems, have also been installed in tunnels. The selection of the appropriate FFFS should be based on cost-benefit analysis. Although tunnel FFFS are used regularly in some countries, they remain the exception rather than the rule in road tunnels world-wide. While such systems can reduce the rates of fire growth and spread, they also demand a higher level of maintenance and operational attention to ensure they function in an optimal manner.

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8.8. Systems for surveillance and control of traffic A traffic surveillance system is often installed when the level of traffic is very dense in a tunnel. Usually, a video-surveillance system is used, supplemented sometimes with counting devices. A video-surveillance installation offers the operator the possibility of controlling the traffic conditions in the tunnel in real time. In case of degraded operation, it allows viewing the concerned incident zone so that the needs may be rapidly evaluated. Video-surveillance is thus a very valuable tool for the operator because it allows him, on the one hand, to watch continuously the incidents inside the tunnel and on the other hand, to react rapidly in case of need. However, in order to make full use of a video-surveillance installation, it is essential to maintain a human presence, if possible continuously, at the control-command centre. A video-surveillance is generally quite simple in its conception. Cameras placed at regular intervals in the tunnel provide a complete coverage of the tunnel and its surroundings. The images are then grouped and transmitted by networks that may or may not be dedicated, to the control-command centre of the tunnel. The images are then received and viewed on the displays.

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8.9. Signposting Signposting is one of the means available with the operator for communicating with the user. For a given type of road, one can see in a tunnel the same signposting as in open air:   

Fixed directional signposting Fixed police signposting (danger signs, speed limits and destination) Variable signposting (lane allocation signs, variable message signs).

The different safety devices available to the users in tunnel (emergency telephones, extinguishers, emergency exits...) require in addition a specific safety signposting. The principal problem faced for signposting in tunnel is the location. In fact, the geometrical characteristics of an underground tunnel are optimised and increasing the transversal section will lead to significant surplus costs. In practice, a compromise must be found between the need for good visibility of the signs (therefore, panels sufficiently large) and the space available.

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8.10. Barriers When a serious event (accident, fire, etc.) occurs in a tunnel, it must be possible to prevent at an early stage the users from entering into the tunnel. In fact, a device preventing efficiently and rapidly entry into the tunnel can allow not sending into a potentially dangerous situation users who are outside and will also help prevent further accidents underground. In many countries, experience shows that if the tunnel is closed simply by means of a stop signal placed outside before the entrance, it is not quite effective. Therefore, this stop signal is often combined with barriers and variable message signs allowing the users to be informed of the reasons for closure. The device closing the tunnel can be activated from the control-command centre or automatically in tunnels that are not monitored continuously. The closing device is meant for being used in emergency situations but it can also be used in other situations, particularly during scheduled closures for maintenance interventions.

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9. TUNNEL RESPONSE TO FIRE



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9. Tunnel response to fire The materials used in the structures and equipment of a tunnel should neither burn nor produce large quantities of toxic smoke if a fire occurs in the tunnel. In addition, in such an event, the structures must not collapse while users or emergency services personnel remain inside the tunnel and critical safety equipment must continue to function at least until evacuation and fire-fighting operations are completed. These general objectives are dependent upon the reaction to fire of the materials and the resistance to fire of the structures and equipment: 



The reaction to fire of a material characterises its ability to take part in a fire to which it is exposed, including by its own decomposition (e.g. combustion).This is discussed in Section 9.1. The resistance to fire of a structure or a piece of equipment characterises its ability to keep on fulfilling its function despite the development of a fire. Structures are considered in Section 9.2, while equipment is considered in Section 9.3.

Contributors

This Chapter was written by Robin Hall and Working Group 4 of the C4 committee (2008-2011) in which: 

Robin Hall (UK) coordinated the work and wrote the full chapter



Fathi Tarada (UK) and Ignacio del Rey (Spain) reviewed the full chapter.

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9.1. Reaction of Materials to fire The materials used in tunnel construction have to possess adequate resistance to fire to ensure integrity during evacuation and fire fighting. Section VII.3 "Fire reaction of materials" of technical report 05.05.B "Fire and Smoke Control in Tunnels" discusses the fire properties of tunnel materials, indicating that the specifications set for materials should include requirements concerning their properties in the event of a fire. Desirable properties include:   

low flammability, which reduces rate of fire spread; low heat output, which reduces the fire size and hence the structural and life-safety impact; and minimisation or elimination of toxic products of fire.

Gases generated by a fire cannot be prevented, but the risks can be mitigated by the choice of the material and also the design of safety features, such as escape routes, to reduce exposure. Attention is also drawn to the properties of wall-covering materials, including tiles and paints, waterproofing or lighting equipment. The specifications set for such materials should also include requirements concerning their properties in the event of a fire. The possibility that materials might produce chemically corrosive or toxic substances during combustion and that these might penetrate the surface of the concrete and cause subsequent corrosion should also be considered. This also applies to any coatings that might be used. In case of polypropylene fibres being specified to reduce the risk of spalling, the issue of concrete durability after any significant fire event should be considered. This is because there will be increased porosity within the concrete where fibres have melted, leading to increased vulnerability to carbonation or chloride attack. Road surfaces may be constructed from cement concrete or asphalt. The Route/Roads article "Effects of Roadway Pavement on Fires in Road Tunnels" discusses the properties of these materials from a fire safety point of view. Of these, cement concrete is the only one which is not combustible and does not raise any question as to its use in tunnels. However, studies and experiences from real fires have shown that, in phases when safety of people is concerned, asphalt does not add significantly to the fire size (both heat release rate and total fire load) in the case of a road tunnel fire. Open asphalt is not advisable in tunnels as a fuel spillage will be stored below the road surface.

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9.2. Resistance to fire of structures The fire resistance of a structure can be characterised by the time which elapses between the start of a fire and the time when the structure does not ensure its function any longer, due to unacceptable deformation or collapse. Chapter 7 "Design Criteria for Structure Resistance to Fire" of technical report 2007 05.16.B "Systems and Equipment for Fire and Smoke Control in Road Tunnels" summarises the objectives of structural fire resistance in tunnels as follows: 1. people inside the tunnel shall be able to self-evacuate (self-rescue) or be assisted to a safe place (main objective) 2. rescue operations shall be possible under safe conditions 3. protective measures shall be taken against collapse of tunnel structure and loss of property to third parties A supplementary objective is to limit the time during which traffic will be disrupted due to the repairs after a fire. An overview of the subject was published in Chapter VII.4 "Fire resistance of structures" of technical report 1999 05.05.B "Fire and Smoke Control in Tunnels". The fire resistance of structures is described in relation to different time-temperature curves. Figure 9.2-1 shows the ISO 834 curve, the Dutch RWS curve, German ZTV curve and a French'increased' Hydrocarbon curve, HCinc, in which the temperatures are multiplied by a factor of 1300/1100 from the basic Hydrocarbon (HC) curve of Eurocode 1 Part 2-2.

Figure 9.2-1: Temperature versus time curves for ISO, HC inc, ZTV and RWS standards (Routes/Roads No. 324) Design criteria for resistance to fire in tunnels have been agreed between the World Road Association (PIARC) and the International Tunnelling Association, as presented in the Routes/Roads article "PIARC Design Criteria for Resistance to Fire for Road Tunnel Structures" (2004), and published as a PIARC recommendation in Chapter 7 "Design Criteria for Structure Resistance to Fire" of technical report 2007 05.16.B. A summary of the proposals is presented in Table 9.2-2.

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Table 9.2-2: PIARC and ITA recommendations Notes (1) 180 min may be required for very heavy traffic density of lorries carrying combustible goods. (2) Safety is not a criterion and does not require any fire resistance (other than avoiding progressive collapse).Taking into account other objectives may lead to the following requirements:  

ISO 60 min in most cases; no protection at all if structural protection would be too expensive compared to cost and inconvenience of repair works after a fire (e.g. light cover for noise protection).

(3) Safety is not a criterion and does not require any fire resistance (other than avoiding progressive collapse).Taking into account other objectives may lead to the following requirements: 





RWS/HC inc 120 min if strong protection is required because of property (e.g. tunnel under a building) or large influence on road network; ISO 120 min in most cases, when this provides a reasonably inexpensive way to limit property damage; no protection at all if structural protection would be too expensive compared to cost and inconvenience of repair works after a fire (e.g. light cover for noise protection).

(4) Other secondary structures: should be defined on a project-specific basis. (5) In case of transverse ventilation. (6) Shelters should be connected to the open air. (7) A longer time may be considered if there is a very heavy volume of lorries carrying combustible goods and evacuation from the shelters is not possible within 120 min.

The consequences of failure will influence the requirements for fire resistance. This depends on the type of tunnel. In an immersed tunnel, for example, a local collapse can cause the whole tunnel to be flooded whereas local collapse in a cut-and-cover tunnel may have very limited consequences. A basic requirement is that progressive collapse must be prevented and vital longitudinal systems, such as an electrical supply or communication cables, are not cut off. The materials used in tunnel structures involve different precautions for fire protection. Section VII.3 "Fire reaction of materials" of the report 1999 05.05.B "Fire and Smoke Control in Tunnels" discusses the characteristics of rock tunnel linings versus reinforced concrete. The intensity of the heat generated during a major fire may cause reinforced concrete to lose its supporting function. The role of insulation using fire-resistant protection can be applied to prevent early damage to the structure. The fire resistance of the total construction (type and depth of reinforcement/prestressing, additional protection, etc.) needs to be considered. Spalling of concrete is caused by differences in temperature and expansion. It causes a danger for the reinforcement which is more easily exposed to high temperatures. It will generally not be a danger for


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evacuating people, but it may be dangerous for firemen. Various types of fire-resistant protection can be used to reduce the risk and the effects of spalling, although it never can be completely prevented due to the high temperatures that may occur. Attention must be given to the fire resistance of the ventilation system so that its design performance is not impaired by failure. Therefore it is necessary to examine the consequences of a local collapse of a duct in case of fire. Escape routes are only used during the first phase of the fire for the escape of trapped people. It must be possible to use such routes for a period of at least 30 minutes. In cases where these routes are also used by the rescue and fire teams, the period may be longer. To avoid fire spreading into an adjacent tube or escape route, emergency doors, emergency recesses and other equipment located between two traffic tubes, should remain intact during a specified period of time. The whole emergency door and surrounding construction, including the door frame, should resist fire for at least a 30 minute fire exposure. For a door between two traffic tubes, a much longer resistance is required, for example 1 to 2 hours.


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9.3. Resistance of equipment to fire In terms of resistance to high temperatures, tunnel equipment and cables can be broadly grouped as either fire-rated or unprotected. Protected equipment and cables with variable levels of resistance to fire include, for example:   

fire-resistant cables capable of withstanding 950°C for 3 hours (CWZ specification); LS0H cables: 250°C for 3 hours; ventilation fans: 250°C for 1 or 2 hours

Unprotected items of equipment such as traffic signs, cameras and public address (PA) speakers have working temperatures typically up to 50°C, and are likely to fail at relatively low temperatures. Materials include: 

  

luminaires - laminated glass (fluorescent) or toughened glass (SON); aluminium alloy or steel housings (working temperatures for SON luminaires typically about 120°C) traffic signs - polycarbonate screens, stainless steel housings cameras - lenses, aluminium housings public address (PA) horn speakers - glass-reinforced polyester (GRP).

Critical temperatures for materials used in such unprotected items include: 

 



polymer-based materials such as polycarbonate will melt at temperatures in the region of 150°C and ignite at temperatures in the order of 300-400°C; silicone sealing - working temperatures typically go up to 200-250°C; glass - working temperatures for toughened glass are typically up to 250-300°C, cracks may develop at temperatures greater than 600°C; aluminium alloy - softens at 400°C and melts at 660°C.

All fittings used for the fixing of equipment to the structures should be considered in terms of their behaviour in fires.

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GLOSSARY


Road Tunnel Manual-piarc

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